On all the bikes I build, the chains are ridiculously tight out of the box. In my experience outside of BMX bikes, this leads to quick chain wear, chain ring and driver wear, and bottom bracket wear. So I loosen the rear bolts and give the chain some slack. Not floppy slack, just enough so the chain doesn't feel lock a solid steel rod.
I understand that with jumps and drops, you need the chain a bit tighter than on another style of bike to avoid the chain dropping.
Am I missing anything here? Is there a reason why I should leave the chain in this hyper-tight state when I build bikes?