Not carrying a tube because flats are rare is like not wearing a helmet because you don't plan on crashing.

I suppose your motivation for racing is what determines your particular answer. Are you in it for the "podium experience" or are you in it for pride? I've done very little racing, but when I have it is an issue of pride for finishing. I've had chains that broke multiple times, repaired and limped in. And I was absoluetly pissed off when a tire had an exposed bead and busted all my tubes. I DNFd. ONLY time I ever did that.

If you're embarrassed by a DNF, I suppose you'll carry a tube. If you're one of those whiner types who believe if they can't finish in the top 10, then you won't finish at all, then I suppose there is no need.