There are a few issues that can crop up by circumventing Airbnb/Vrbo/HomeAway.
By bypassing the hosting website and renting directly with owner, will make you lose any claim for double booking, won’t have insurance and other issues.
I rented a house in North-Conway New Hampshire, 4 summers ago, and went thru the hosting site (didn’t bypass). And on the 2nd day we had a family of 4 “shchorim” come, saying that they rented it. The owner confirmed that he did rent it to them, but after we booked it. We let him know that if they enter the house, we’ll call police, and file a complaint/breach of contract with Airbnb (HomeAway/Vrbo or whichever company it was).
Had we rented directly with him, we wouldn’t have those recourses.