They don’t need to. Their are a bunch of officials there for that purpose. In golf, there are only you and your opponents in your group, so it is much more up to the player.
I don’t think golfers have anymore integrity than other athletes. It is just the nature of the sport to self regulate.
I played hickories for a number of years and generally had 9-10 clubs in my bag. Switching back to modern clubs, I found that with age and stronger lofts, it took about 6 - 8 degrees of loft change to get a 10-15 yard differential. As a result 8-9 modern clubs seems to cover my spectrum of distances without creating any big distance gap. Also makes for a lighter bag when I walk. 😀