Obviously practicing more generally means fewer mistakes, but I think there is an element of brain wiring/personality type involved as well. There are some players who are just machines (and I mean that in a good way): They just seem to make very few mistakes. Sometimes they are not even necessarily great musicians.
I know one guy who plays in a number of classic rock cover bands: Nice guy, but He's kind of a hack: he often does't play the original baseline to the songs, just generic chord-root kinds of basslines, and does't have a particularly good ear, he just learns his songs by looking at tabs or chord charts off the internet. Improvising is out of the question.
That being said,a guitar player friend of mine who plays in a band with him says that he has never heard the guy screw up-he may not play the exact right baseline, but what he does play works, and he nails it every single time, and that is why he gets so many gigs with classic rock bands.
Now, I do not have that "no mistakes" thing going on, but I still make my living playing and teaching music, because I can do a lot of different things: I can read music, improvise, things up by ear, and play a lot of different styles of music. My guitar-player friends comment on the difference between us was "Yea, you play clams now and then, but you're still a way better musician than him: people know they can hire you for any kind of gig, and throw anything at you on a gig, and you'll make it work, and play some really cool stuff too. He's super consistent, you could break a 2x4 over his head and he probably wouldn't miss a note, but not as much fun to play with; his lines aren't particularly interesting, they just work, and he doesn't do well if we change anything about the song".
Obviously, being a consistent player and a flexible player are not mutually exclusive; the point is that different musicians have different strengths. Les Claypool is a great player, but isn't particularly consistent-but his gig doesn't require him to be. The players who get gigs with TV shows definitely need to have the consistency thing.