Seems to me bodybuiders probably are only concerned with making muscles bigger and so don't lock out as they want that tension to provide more muscle growth.
But, there are other things that are required if your goal is lifting maximum weight. Your bones, tendons and connective tissue all have to grow or thicken too.
If you don't put stress or put much lesser stress on those other elements, you probably won't get as strong as if you did.
As Jim said, that's probably why BB'ers do themselves a mischief from time to time when they do lock out. The other stuff isn't keeping pace with their muscles.
Let them eat cake, I say! I do what I do, others can do as they wish.
I am Anton Zdravko Martin!
Best meet lifts: Sq 150 Kg (330 lb), Bench 120 Kg (264), DL 160 (352) @89 Kg (197)
Best gym lifts: Sq 375, Bench 280 (pause), DL 385 @205 or less
Goals beyond my wildest dreams, 600 Kg raw total, 200/160/240
Hack away at anything which isn't essential. Do what you love, and do it often. Fazc.
Everything competes for recovery so more assistance is not always the best idea. miked96