They do it to prevent botting . They use play integrity ( i think ex safety net ).

Can concert tickets not be bought in a web browser?

No they can’t. It’s very frustrating.

I had to get my friend to buy them for me when I was on Graphene

Nope. This is eplus in Japan, and if you try go through the website it tells you you have to use the app. It's cos a lot of shows these days don't use paper tickets, but smart tickets on your phone. It is what it is.

What about people who do not have a smartphone?

They don't get to go to concerts in Japan.