We do it at UK immigration for some people. It's a bit random. I was questioned before I got leave to remain. Even on short visits occasionally, frequently when I came to be a student. But not always. The thing is that they can do it, when and if they choose, to make sure people aren't getting in who aren't entitled. And sometimes that will end up being a random check, so that they aren't targetting certain groups.
Just because UK tourists are a large proportion of tourism in certain countries historically doesn't mean it will stay that way; those countries might well want to increase tourism from elsewhere, because it's just so much easier to process.
Eventually there will be an equilibrium reached between cost, numbers of crossings/flights allowed, how many people get questioned/visas checked, etc.
With a lot of international rules on visas, money, vaccines etc, the complications are in the researching it all and getting it sorted. You don't often get asked for a lot of things. But you can. And the consequences of not having them can be high, so people do comply, even if much of the time they aren't asked.
Yes, if they chose to insist tourists needed 100 euros a day, they could, and you'd have to be prepared to show that, by whatever means they asked for - could be some kind of pre-authorisation, or being prepared to show banking apps, or printed statements, whatever they decide. Doesn't matter if you don't think you need it or will spend it, doesn't matter if you're staying with someone, if that's what they've decided, you wil lhave to be prepared to show it, because they have the power over you coming in - they will want to make sure people don't come in who can't support themselves, and this could be an easy way to check that. No, they probably won't check most people. But you don't have any right to holiday in any other country, so you'd have to be prepared to show that documentation if they wanted it, regardless of whether you think you need that much money.