Pat,
I realize many have done it for many years as I have seen it myself. I still cringe when I see it.
Sprint cars and Formula cars are regularly taken apart and inspected, (or, at least should be). When is the last time anyone around here took their car apart just to inspect it?
Race car wheels are going on and off; engines are coming in and out...there is just much more opportunity to catch something which is wrong on a race car. I think too many of us put in gas and go for a drive without much thought of anything else.
Bearings are highly stressed components by nature--why add to their stress. If a bearing galls on a race...the race is over.
David