People love to complain about realtors. Companies like Redfin have been trying to disrupt this market for years. People on HN and other places like to complain that realtors are pointless and that the only reason they exist is they are entrenched.
I posit a different theory, which may well be controversial here, and that is that realtors continue to exist--and charge large commissions doing so--because they provide a service that most people want.
I think of it like advertising. "I never watch ads" is a common catchphrase when decrying ads but again, ads exist because they work.
The job of a realtor, and what they are incentivized to do, is to facilitate a transaction. People might point out that a selling realtor isn't incentivized directly to get the best sales price. They are correct. Why show a house 100 times in the hopes of getting $550k when you can flip it tomorrow for $520k and your work is done?
Thing is: that's what most sellers actually want, even though they might say they want the best price. Most of them are selling for a reason and they just need to sell it and move on with their lives.
Likewise, when it comes to buyers, they too are buying for a reason, typically because they need somewhere to live or they want to establish (more) permanent roots in a given community. The best thing for most of them is to pull the trigger, move in and get on with their lives. It's not to get the best deal. It's not to wait 2 years for the perfect property.
Realtors facilitate both sides of this equation.
Have you ever deal with a For Sale By Owner? I have. I refuse. I won't even go and look at a listing FSBO. It's a nightmare. Those owners tend to be cheap (hence not paying commission), have unrealistic expectations of their property's value, overvalue whatever "improvements" they've done and, worst of all, are emotionally invested so they re more likely to take a lower offer personally rather than as a negotiating tactic.
It's worth noting too that with negotiating in general, it's often better to have someone else do it for you. If you're the guy who can say yes or no you have no fallback. If you represent that guy you now have the position of "my client won't accept that". Think about the psychological difference of rejecting someone personally or just being the messenger.
So add fixed-fee home sales to the other startup traps like dating sites, travel sites and anything to do with "fixing recruitment" (you'd be surprised how many cold call emails I get about this one in particular). Hell, let's add blockchain to that list too, but I digress.