Raid lockouts are standard in MMOs because players can clear content much quicker than it can possibly be developed.

If Coil was on a weekly loot lockout instead of a regular weekly, then groups would farm various turns for gear until everyone gets something. This would shorten the lifespan of the raids as you could in theory gear up an entire raid in ~6 weeks at the 2 drop/boss rate if all turns share the same lockout, or gear an entire raid in 2 weeks if they don't. The alternative to that is that they reduce the rewards, but that just makes the game more RNG and more frustrating as drops are now going to have to be balanced against the expectation that you are running multiple times a week.

It is true that raiders that finish content do tend to fall into a pattern of logging in once a week to raid, then never log in again, but if they are able to max out their character in a few weeks in content that is supposed to last 6 months, they will just get to that point much faster.