First, you don't HAVE to use this function. I never do on fallout New Vegas. I prefer to walk everywhere (excluding missions where it's just going back and forth large distances.)
Second, you have to discover the place first, am I right? So Yeah, the fast travel may take stuff away from the experience, but with the first point in mind, you have to actually explore to discover the fast travel point anyway, so you are always going to see a lot of the world by this means anyway.
Third, Fast travel is useful for the less hardcore player that wan't action instead of trudging through a wasteland for hours. I know I did when I got oblivion. I wasn't even aware that fast travel existed, and was over the moon when I realized it did. Because I found myself getting really, really bored. Thus, I didn't really want to play anymore- The fast travel saved me of that, it meant I could zip from action scene to action scene if I wanted, and explore if I wanted.