Cause hardly anyone re-uses anything! We have become a throw away society!
Biggest problem with most pallet/crate wood is box nails. Spiral shank nails that are designed to NEVER come out. Especially if they are in hardwood. Might want to pull one apart to see what it takes before you commit to doing hundreds. I have already cut the thin boards close on top. Then split the remaining part that is only the width of the other board so the pieces break away from the nails. Then either hammer the nails in or cut them off. Or nick them and they usually break pretty easy. Angle grinder with cut wheel knocks them off quick. It won't be easy, but if the savings is worth the time...