The reasons I'm on 56K are:
1...I can't get broadband at all (short of a T1, which is out of the picture, in terms of cost)
2...They never will install it in this VERY small town. We're at least 30 miles from any decent sized city in all directions.
3...There is fixed wireless, but a 64K connection is almost $100/month! And they include a dial-up account with it for free (well, they say...), so you know it has to be unreliable enough to warrant that.