>* dating apps aren't the only way to meet people; you can still meet potential partners at parks/bars/work (Americans love office romances apparantly)

Think about doing a job search. You could find a potential employer at a park/bar/whatever, but it's a lot more efficient to go to a job site where people are actively looking to employ you. It's similar for dating. It's definitely possible to meet someone to date in the real world. It's just a lot less efficient than doing so in a space where the only people there are those actively looking for the same thing you are.

Plus, people typically go to the same bars/parks and have the same circle of friends. The absolute number of single people will be relatively small and you can go through them relatively quickly. There's also the awkwardness of dealing with failed relationships.