They're illegal here... But I still get about 5 every day.

US gets a lot of robocalls for a few reasons: the target population is large and one or two languages addresses the vast majority, easy means of payment from victims, high trust society, and maybe most importantly near zero cost of calling. I read something from the FCC several years ago that call charges between carriers would soon be set to zero, rather than the previous status quo of something around a penny per minute for terminating calls, netted out. Commercial services charge around a penny or less per minute, and anything with volume can get to much less.

UK, US, CA, usually run by scammers from countries with low income and weaker currencies. They target countries with gullible, often elderly, population groups that have access to cash in a stronger currency to make the biggest profit for the least effort. Huge benefit of the robocaller is that they can sound less scammy because your first point of contact is well spoken relative to the scammer who often has a thick accent.