I have flipped houses for years and have gone through every auction process imaginable plus worked for an auction house.
Blind auctions are used when there is a very finite group of buyers. Or in some cases you know exactly who the buyers are and the buyers might also know each other.
A traditional auction is used when you have a property in normal range in a decently populated area that will have a good amount of interest. For 90%+ of the properties a traditional auction with the right promotion and auctioneer will get you a much much higher return.
Let's take some use cases for a blind auction. Let's say that you have a house that is $1millon+ in a small town. The house may be a commodity in that there aren't many like it but again in this small town there aren't many people that can afford it. You don't want 3 guys showing up to your traditional auction. Within 5 mins these guys could have a side deal to limit the sale price of the house or just recognize that they are just bidding each other up and stop.
Well you might say well they can find each other for the blind auction too. Well maybe but probably not. I had thought I had done this several times when buying houses - colluding with other flippers - to find the one guy we didn't know about outbid us (and get something at 80% of market vs 70%). And in my opinion it is rather easy to manipulate blind auctions. The seller can usually always say that this person bought it at a higher price if a low price actually won.
Now why are real estate agencies doing blind auctions in your area. First there could be a real estate frenzy there especially with certain home types and they are hoping that paranoia will take over and people will reach much higher than market (this same thing would happen at a traditional auction too). They could also be trying to play a "cool" factor. I am guessing they wouldn't do this for the 150K two bedroom dump in a shady area.
But really why wouldn't a real estate company do this if sellers let them? Their costs is mainly their time. Their profit has little to do with what price you sell your home. So let's say you have a 900k house and because of the blind auction you only get 850k... not a big deal to real estate company because the time and money they saved on not having to sell your house traditionally offsets the small percentage of commission lost at a 50k difference.
To the average (uneducated) seller the real estate company wins no matter what. If the seller gets 850k for the home the real estate company tells them reasons why their house wasn't worth 900k. If they get 900k they tell them - look how quick we sold it (no shit its an auction). If they get 950k they say, see how the blind auction worked! When in most cases the blind auction probably reduced the final sale price.
The only two things a blind auction are good for is to separate colluders and to allow people to bid without having to provide proof of payment ability. In some traditional auctions you have to either bring "cash" or proof of ability and you would be capped at an amount.
What I would suggest and it seems that any reasonable real estate agency would do this is to not do blind auctions but to do blind bids for a week. I have sold many houses this way and it is the quickest and most profitable. It is not meant for a fixer up but works for a "good" house. You simply let people bid blindly and allow them a certain amount of bids per day or week. You can tell them on the spot if there bid is accepted as the high bid. At the end of the week if they are not the high bidder they are allowed to bid one more time. House sold.
So to answer your question... Of course the real estate agencies benefit. Did you think it would be any other way? And of course if they benefit guess who doesn't benefit?