Because you have a poor ISP. No proper ISP should block anything (except maybe child porn, but that's a slippery slope). Change your DNS to either Google's (8.8.8.8) or OpenDNS.
If you live in a repressive country prohibiting pornography you should get a VPN. I'm satisfied with my choice of strongVPN.com
#2 is patently false and the biggest reason I don't try to train people not to use Google as their URL bar. It is not cool when a tween kid tries to visit the Poly Pocket web site and finds something very different.
#1 is partially true. It won't block somebody trying to get around it, but it will prevent #2 from happening.
And a breast is the least of concerns with some of the trash parked on misspelled domains.
If you live in a repressive country prohibiting pornography you should get a VPN. I'm satisfied with my choice of strongVPN.com