Can somebody enlighten me why robo-calls are such a problem in the US? I'm completely ignorant of any relevant legislation or enforcement, but as a young German I can literally remember exactly two unsolicited survey calls in my whole life, both on a landline.

This suggests some fundamental difference compared to the US which maybe should be changed instead of a third party band-aid app with lots of problems, but again I don't know this difference and thus will refrain from judging...