Why don't company's like Comcast give loyal customers discounts?

A little over a year ago, my husband called (re: cable service though) and threatened to switch to Direct TV (having heard this is an effective way to get a pretty good discount and/or free premium channels for a stretch of time). The person on the phone told him to switch!
However, we are the only people I've heard about that happening to; everyone else has gotten a deal of some sort. Try calling and say you're considering a switch to Verizon DSL or something else. I guess they figure, if you buying at the regular price, why reduce it - unless you give them a reason to. For us, Comcast is pretty dependable in terms of internet service, and I wouldn't want to switch to a slower DSL.
We actually wound up with Comcast digital voice, too. Since we already had cable and internet, it actually costs us less to have all three, and now we have HBO, Cinemax, and Showtime, too. You might want to look into that.