I think my Dad had a similar experience for Who Wants to be a Millionaire, which he applied for many moons ago, but he didn't hear back either. I suppose it's inevitable that the number of applicants is many times higher than the number of people who actually appear on the show. Also there's probably a selection process that prunes some of the higher scorers out, so you might be better off trying to get 6/10 and sounding vaguely interesting than getting 10/10 but sounding like a boring old fart.
I put down that I was on UC when I applied to The Chase. It's not impossible that this counted against me, although I would need at least one other decent team-mate to threaten to win anything really -- too many gaps in, eg, television and pop music.