I don't believe they would do that. They know we know there are both honest and dishonest hosts, but they prefer that it is us who take the risk. Based on the reviews, apparently.
That's not what happens when you're a monopoly. What happens is the people just eat it.
You can see it more clearly in politics. Does anyone think politicians have the people's interest at heart? The answer is it doesn't matter, because people have proven that they'll just eat it, for decades.
But they're not a monopoly at all. There are countless other ways to find lodging, whether short term or long term, and even the market for app-powered short term letting like airbnb has very low barriers to entry so someone with enough capital (harder in the current environment, but eventually doable) can come in and outcompete them
Would you mind sharing some? I only know of Booking.com, the rest are country-specific billboards at best. E.g. Craigslist in the US, Bazaraki on Cyprus or Avito in Russia. In all of them you'd better view the apartment in person first, and you manage your own contracts and payments.
Fortunately, that's not exactly correct. After getting burned a few times with AirBnB I now use booking.com mostly. Of course they are evil in their own ways, but the percentage of incidents is much lower for me.