You can't really improve your position when a submission is locked in , so tapping is just acknowledging that your opponent got the better of you. If you don't tap in that situation and your arm is broken ala Mir/Big Nog, Mir/Sylvia, Saku/Renzo etc then it's just a sign of poor sportsmanship on your part and you're probably deserving of a broken limb. Tapping to strikes differs though, if you're trapped in a crucifix I can understand or in a similar predicament to Barnett when he lost his vision and didn't want to be punted full force by Cro cop but tapping the way GSP did to Serra was just an easy out for a guy that severely underestimated his opponent. That kind of tapping to strikes I strongly disagree with, kudos to you if that's how you want to go out but I don't agree with it.