I guess you've never staked then.
If you have 2 accounts with the same attack, strength and hitpoints, one has 1 defense and the other has 15 and you're doing dds to dscim no move, you're not going to have any advantage.
AND if you're xing cause of your 15def, which most people will want you to, you're going to lose in the long run. Even if you're not xing, you might still lose in the long run if you're unlucky with hits and pid. Trust me that 15 defense ain't doing shit, it's still 50/50.