One reason why I bought my own domain ...
I have a hotmail account <myname>@hotmail.com from 1996. It used to be a nice subtle indication that I was there when it was still fields.
But quite aside from the dangers of name collision*, I have to trust Microsoft to manage my email ? Fuck that. The final straw was the perplexing inability to get the calendar working with any decent Linux desktop. But at least I own the whole lot.
*Despite having an unusual name, there are still a few exact matches in the world. As a co-worker discovered trying to Google me, and telling colleagues about a conviction I had. Only I hadn't - that was a US version of me. Cost them their job, sadly.