I'm in the 'not-a-fan' of defoliation 'just because' camp. Unless you are doing a tight SOG or SCROG or something where you're trying to push some limits in using every inch available and know you will run into crowding issues like with mold or something... But keep in mind when you flip to flowering, they're going to stretch and what looks bushy now won't stay bushy. But that's, like, just my opinion on the subject man. Don't really think it hurts the plants much either since most growers provide their plants with more than enough nutrients to replace what was stored in the leaves and then some and the plants will replace what was lost pretty quickly (which includes growing more leaves).