There's no reason that holds water, to disable the ABS on a track bike provided that it is a modern and good system. Plenty of excuses - but no reasons. The good ABS systems won't interfere with your normal riding ... and the ABS is there to bail you out if you make a mistake, just like on a street bike.
Some of the old ABS systems that were only capable of "on/off" operation and which sometimes false-triggered prematurely might have caused trouble, but I have a bike with a modern ABS system (KIBS, in this case) and I wouldn't think of disabling it. It doesn't chatter, it doesn't interfere when not needed, the bike just plain stops.
You haven't told us make/model/year ... it makes a difference ...