This is kinda like the argument between an authoritative government and a democratic one, the former works great until it doesn't. When it works, the former is more efficient and can get things done much more quickly but when things go wrong it can go horribly more wrong as well because the checks and balances aren't there.

I think it's a matter of stakes. In UI design, while the risk to the business will vary case by case it's almost never as costly as the risk in governing. Committees just aren't great at moving fast, and in UI design moving slow might be more expensive than moving in the wrong direction and learning something.