Not quite sure myself as I am currently on the receiving end :D.
I would say this though that, 4 screens, hackerrank, take home coding, onsite format is not limited to big tech companies. I've had to do that for local smaller shops too.
Anectodally, it seems to be a lot worse in the US. But why would it ? I would have thought the competition for great engineers is highest there. Humiliating them is not the best strategy...
The pay is high in the States. Many companies are willing to pay a steep premium for slightly stronger employees, and the candidates are more willing to jump through hoops to land a higher-paying job.
Not the whole story of course, but might be a factor.
I would say this though that, 4 screens, hackerrank, take home coding, onsite format is not limited to big tech companies. I've had to do that for local smaller shops too.