I think that it makes a lot of the driving look a bit ungainly & unbalanced a lot of the time.
That being said I don't think unloading on a horse is the best way to get it rolling anyway so that's a small price to pay. The really talented drivers I've seen over the years don't need to flog them to get them to give their best. Loud noises, shouting is just as good or a couple of serious cracks of the whip on the wheel disk/shaft/dust sheet even, that does a lot more to shift them than slashing away like some half arsed Samurai.
I can remember the not so long ago bad old days where they'd come off the track with welts on their rears, sometimes pretty decent sized cuts etc. and some of the really mean pricks around thought nothing of landing really hard stifle shots on them etc. Good riddance to all of that. Thankfully I haven't seen anything that was even remotely like it in recent times.