Wondered about that myself when I had DSL. Truth is, my cable and internet connection is more reliable than DSL ever was. Not a problem, IMO, but YMMV...
The cable TV in that house goes out at least once every other day, for ~1-2 hours at a time. Doesn't matter what the weather is. I suspect I'd have been sucking the hind one on inet service at those times as well. I'm sure it's related to the really cr4ppy cable infrastructure Dallas has.
The house has a homerun from the telco NID to the DSL jack in the computer room (still have a server farm there). The splitter would short for months on end, causing the dial tone & voice service to die, but had no effect on the DSL frequency. The DSL has been rock solid, thru an RT that's a block or so away. Never really cared about the voice line anyway.