Because most people that seem to try are trying to crack the relatively easy part, which is the actual payment. If all that you needed to do was have a small amount of money go from a site visitor to a site operator with nothing else affected or involved or triggered it would not be hard.
The hard part is running an international business, and that is what a web site that accepts micro payments (or macro payments) is the moment someone from another country pays for its content.
When a site visitor pays a site operator, regardless of whether it is a micro payment or a macro payment, and regardless of the mechanism used, that transaction might:
1. be subject to sales tax or VAT by the visitor's government, the operator's government, or both,
2. be subject to tariffs or duties if the operator and visitor are in different countries,
3. be subject to reporting requirements or other paperwork due to sanctions if it is between countries,
and probably many more I'm forgetting.
Even if you just sell in one country it can get annoying. In the US sales tax when you sell to someone in a different state is due in the buyer's state, but the seller has to collect it. There are thresholds below which there is no tax, but unfortunately many of them are of the form N transactions or X dollars, with N around 100. If 100 people in such a state do a $0.01 micro-payment on your site that's $1 of revenue but you have to collect and report sales tax and it is probably going to cost you more than $1 to deal with.
To avoid all this what you can do is to have an intermediary between the site and the visitor with that intermediary being the seller that they buyer deals with. In other words, a store that carries the content from many sites.
The site is then just selling to one entity, the store, so at most had to deal with keeping two governments happy (its own and the one of the country the store is in). The store deals with all those issues of selling to people in hundreds of different jurisdictions.
Notice with the store model you don't actually need micro payments for the visitors. I think most people would be OK with a model where they could buy credits in multiples of some small but not micro amount, say $1 or $5, and then use this credits to buy content from site for micro amounts. And the store doesn't really need micro payments for the sites, because the store is aggregating all of the payments to the site. It can wait until the site accumulates enough for a macro payment.
But there would still be a role for micro payments in this model. With the macro payment for credits approach the visitor has to have an account at the store. If there were too many stores you might need accounts at dozens of stores to cover all the sites you are interested in. Ugh.
With micro payments to the stores you could probably get rid of the account requirement.
Because most people that seem to try are trying to crack the relatively easy part, which is the actual payment. If all that you needed to do was have a small amount of money go from a site visitor to a site operator with nothing else affected or involved or triggered it would not be hard.
The hard part is running an international business, and that is what a web site that accepts micro payments (or macro payments) is the moment someone from another country pays for its content.
When a site visitor pays a site operator, regardless of whether it is a micro payment or a macro payment, and regardless of the mechanism used, that transaction might:
1. be subject to sales tax or VAT by the visitor's government, the operator's government, or both,
2. be subject to tariffs or duties if the operator and visitor are in different countries,
3. be subject to reporting requirements or other paperwork due to sanctions if it is between countries,
and probably many more I'm forgetting.
Even if you just sell in one country it can get annoying. In the US sales tax when you sell to someone in a different state is due in the buyer's state, but the seller has to collect it. There are thresholds below which there is no tax, but unfortunately many of them are of the form N transactions or X dollars, with N around 100. If 100 people in such a state do a $0.01 micro-payment on your site that's $1 of revenue but you have to collect and report sales tax and it is probably going to cost you more than $1 to deal with.
To avoid all this what you can do is to have an intermediary between the site and the visitor with that intermediary being the seller that they buyer deals with. In other words, a store that carries the content from many sites.
The site is then just selling to one entity, the store, so at most had to deal with keeping two governments happy (its own and the one of the country the store is in). The store deals with all those issues of selling to people in hundreds of different jurisdictions.
Notice with the store model you don't actually need micro payments for the visitors. I think most people would be OK with a model where they could buy credits in multiples of some small but not micro amount, say $1 or $5, and then use this credits to buy content from site for micro amounts. And the store doesn't really need micro payments for the sites, because the store is aggregating all of the payments to the site. It can wait until the site accumulates enough for a macro payment.
But there would still be a role for micro payments in this model. With the macro payment for credits approach the visitor has to have an account at the store. If there were too many stores you might need accounts at dozens of stores to cover all the sites you are interested in. Ugh.
With micro payments to the stores you could probably get rid of the account requirement.