I think it'd be annoying. I want to get to the race, not spend 2-3 minutes doing a slow lap on a track I've been running race after race all evening anyway, plus running for countless laps begging for a restart after a race ends, etc.. So -1 from me in general, but for the leaguers that want it, why not? It might be fun now and then on a big race.
One thing that drives me nuts about other sims is that racing is actually rather rare on public servers. Far too many times in rFactor and GTR I've run practice, qualifying, warmup, and whatever else for an hour only to do a measely 8 minute race at the end of it. Sit at the PC for 4 hours and spend 20-30 minutes actually racing. Wash, rinse, repeat. I don't need to practice for another hour again on this track tonight in preparation for another 5 lapper. Ugh.
LFS for me shines largely because the racing is much more immediate and common. Adding a parade lap to me just pushes things away from that, albeit by only one lap, so I wouldn't cry too much about it, I suppose
Might as well have the option to do it though if most people want it.