That they can afford more, I would assume, is because things are cheaper.
clarified belowTo me it feels like quality of living per dollar has risen tremendously over the past generation, but income per household hasn't. So while quality of living overall has improved, it doesn't 'feel' like it with regards to individual wealth. That is to say, an upper-middle class person 15 years ago might feel lower-middle class today even with a better QoL overall.
I would definitely agree that this kind of stagnating income in the middle class is a large part of what is pushing these nationalist/populist movements.
It's definitely not a popular sentiment on HN at the moment(nationalism), but I can definitely see the allure; especially for the lower-middle class who have lived through the past ~15 years and aren't seeing the same increase in wages/authority that the previous generation did.
Personally I have yet to see a real cogent argument for why globalism would help here at all with regards to the growing income inequality in developing nations. From my perspective a single centralized government(e.g.: the EU) can only really benefit the multinational corporation and almost by definition be of detriment to the individual nation-states.
It's hard to really grok the reality of the situation from unemployment/income statistics because they don't really tell the whole tale and of course because I'm neither an economist nor a statistician.
Lastly, I don't think it can really be ignored that this is the fastest changing world our species has ever had to adapt to.
I love technology, of course, but I don't think it's impact has been _only_ good. Looking at pictures of previous generations you can't help but notice the upright postures and healthy bodies that are so often missing from today's populace. Not trying to be a luddite here, and you can of course so,
Edit: to clarify 'because things are cheaper', I'm speaking of disposable items and food, as was stated by another commenter "stuff you can buy in a store"
In fact, I think an important aspect of this discontent is the increasing cost of housing/healthcare relative to income.