For starters, if you arbitrarily round Fahreinheit numbers up or down (which you did to get that 0-100 range), you need to do the same with Celsius. So it'd be -20-40, which is a lot less un-intuitive.
But also, that this range is what "most people regularly experience" is also rather arbitrary. I have regularly experienced winters below -20 C, for example, but I've only seen +40 C once. The truth is, most people will experience a range of temperatures that's not going to be nice and round numbers in either scale, so why fixate on it?
I'm not really saying this is better than Celsius, just that it's understandable why it's not changing as quickly as some would like. I will say that the industries that have specific reason switched fairly quickly. For instance, aviation uses feet, inHg, statute+nautical miles but does temperature in Celsius because pilots overwhelmingly care about whether it's above or below freezing outside.
I'm not saying we shouldn't have switched over decades ago, but I think it's good to understand the context of such decisions.