On a limited deal where they have to manage a bunch of tire kickers I’d imagine it compensates them for their time. If you have one of a certain hot deal it may be just as much work as 5 regular deals at a smaller fee.
But I agree, vote with your wallet and hack your own deal if you have the bandwidth to do it. Brokers help benchmark what’s possible for us to go try to get it done on our own for free.