You'll see some teams/players run anyway in a less than 2 out situation, some from just not knowing the rule, and some do it to try to take advantage of the defensive team not knowing the rule. Granted, the batter-runner will still be out, but they run anyway to try and get the catcher to hurry a throw to first and maybe make a throwing error which allows any other runners to advance on the error, which I believe would be legal. Anyway, I've see it work.
Rulebooks are great. The NFHS book is pretty cheap if I remember, maybe 7 or 8 bucks. Every coach should have one, in fact I think players should also.