If you're in a culture (locality + industry) where a position can be filled in 4 weeks, that's one thing. If you're in a culture where every experienced person has 3 months of notice, then nobody would take your inability to fill a position within weeks to mean that you don't really need it.
I have some experience with part-time contracting with US customers. Seeing how quickly people can join or leave there is certainly a culture shock!
We have a bunch of employees in Europe and everyone involved except the very marginal employees sees this situation as strongly negative (and, in fact, an argument to not hire in Europe at all).
I don't need my 3 months now. They might be useful if my employer axes a whole department. They're useful for people with family commitments giving them less mobility.
What you might not realise is that these three months would be the default legal position in case of disagreement. If you want to leave earlier and the employer agrees, you can usually leave earlier, too (with them being off the financial hook).
It wasn't a problem. I was on good terms with the previous company (I'm still getting invited to their anniversary parties and stuff like that), so there was no issue in working something out.
Also, remember that ~6 weeks of vacation per year is common outside the US, so often it boils down to taking your remaining vacation. (Though I think you need to be careful with taxes and other regulations if the contracts overlap.)
Oh, I agree. But 3 months seems crazy to me. If I have an open position and it isn't filled in ~4-6 weeks, it often gets given to some other team (on the basis that if I really needed that position filled, I'd do so). I can't plan hiring over that timeframe.
And when hiring employees in India, we've had them claim a 2-month resignation period, but they just end up using that time to find some other opportunity on the previous employer's time. It's a real mess.