That's very true, actually, lucky. People who set up their files for SP gain are prepared to take advantage of that SP gain, and often, they depend on it. However, it seems that people aren't often prepared to work around SP drain... For example, any file that sets a Lv1 and then a Lv3 find their opening quite screwed up if they're faced with a turn 1 Shade. Same with those who plan to spend SP on action skills on a given turn, only to have it sapped and essentially wasting a turn. However it does take a lot more skill to properly time SP drain.