You use the stop watch to time classes ahead of you so you know what the track is doing to help you decide tire selection for your race.
The above advice has been given before on here probably by racing promotor and it's some of the best advice you'll ever read on here so IMHO, take it to heart and remember it for ever.
In addition to what racing promotor gave except for what the results of time trials indicate toward the rest of the racing night I never ever care about or look at lap times.
period end of story.
I do though through out any race I'm watching whether I have and entry I'm working with or not check times thru corner entry and thru exit. For me from experience watching racers between the end of entry and the start of exit does not need to timed to see how they do maintaining momentum and setting their exit position.
I pick two spots or markers on or off the track like a light pole or something and do my own one thousand one, two thousand two, etc., to compare differences in time per how they got thru either entry or exit.
For me the fun is always about knowing about the setup of what's on the track and either seeing perfection or near perfection at places around the track or finding even hidden on track problems which need addressed.
If you can identify perfection, near perfection, correctly identify on track problems, the likely why it happens for each and a logical dynamic reason for the good or bad, even top world class racers and crew chiefs will talk to you about it.
The really fun part is when what's raced is again put on the track, you know what has been done to it and why it was done.
It's total fun to go to a race and know the setup of some of what's out there, what is done to change it and then see the results without even having to get your hands dirty. ...
All that to say you need to know what your putting on the track, the reasons behind what you put on the track and then it's all about properly identifying on track problems. If you can do it you then have a chance at getting faster next time out.
Why is racing like shooting pool, golf, archery, throwing darts and other personal goal achieving contests.
answer: There all the same because in each "your never as good as you think you are". ...