I'd agree with you because most of my friends are bloggers and they use wordpress.com. Except for its interface (which looks very basic to me) I think it ranks highest amongst the rest.For me, it's always wordpress.com out of the three. It has all the add-ons and plugins, and lots of free premade themes. I never got on with tumblr, but they are better about having ads on them. They are free, so why not try them and see what works for you?
I think that maybe more people used to use blogger, because it was the most obvious choice for blogging. However, now that there are sites like wordpress.com, people tend to gravitate toward those.I'd agree with you because most of my friends are bloggers and they use wordpress.com. Except for its interface (which looks very basic to me) I think it ranks highest amongst the rest.