I see a lot of people do the practice round thing and IMO it's completely unnecessary given it would have had little if any effect due the the way the system works. A few strokes either way doesn't create a lot of movement. I suppose the exception is the person with so many "practice rounds" that it would have eventually crept into the lowest 10 because their lowest 10 aren't a regular occurrence. Even when I've had a bad stretch and some higher differentials start to replace lower ones as they become part of the last 20 the movement is minimal because the lowest 10 tend to be grouped pretty tightly once you've been at it a while. If something higher gets in the mix it's not drastically higher.
Personally I want a record of it. I can't see the purpose of all the practice if I can't monitor progress, the scores and differentials are the result of that. I'm not super serious about golf but I don't want to log on and see scores and differentials that aren't indicative of how I really play. Most of the time the higher stuff is just a really bad day or the first time around a difficult course. I've put up some high scores recently, high for me anyway, that became part of the best 10 because the course rating was so high. An 82 from the tips at the course I play most frequently is just .93 higher than an 88 from the middle tees at my parents club. It's a private club with tough conditions, I expect a higher score here and there. People tend to forget it's more than just a few strokes.