>WhatsApp can only use data, which is cheaper and used to be unlimited (that's gone) in the EU. In contrast, texting was and still is insanely expensive in the EU (per byte it is staggering even, compared to normal data).
You need to specify where in the EU, because it doesn't mirror my experience in France for instance. Data used to be very expensive while there were no shortages of plans with near-unlimited texts. It also isn't the case in many other countries in the world in my experience. AFAIK the advantage of WhatsApp over plain texts isn't that it's cheaper per-se, it's that it works over wi-fi which means that as long as you find a hotspot anywhere in the world you can use it. No need to worry about roaming fees, no need to worry about how many texts or MB of data are in your plan.
In the Netherlands 10 euro for truly unlimited was commonplace. I held on to that plan from 2011 until last year, when they decide I couldn't have 4G and unlimited data.
You really don't need to specify where in the EU, because there are vastly more people in France communicating regularly with people in other neighboring countries. If you need to specify where in the EU, then you need to specify where in the US as well, because France is about the size of a single US state.
Americans mostly talk to other Americans, who also have unlimited texting plans. French people are probably talking to people who live in Belgium, Germany, the UK, Spain, etc. who will all encourage them to use WhatsApp.
You need to specify where in the EU, because it doesn't mirror my experience in France for instance. Data used to be very expensive while there were no shortages of plans with near-unlimited texts. It also isn't the case in many other countries in the world in my experience. AFAIK the advantage of WhatsApp over plain texts isn't that it's cheaper per-se, it's that it works over wi-fi which means that as long as you find a hotspot anywhere in the world you can use it. No need to worry about roaming fees, no need to worry about how many texts or MB of data are in your plan.