The vacation rental companies offer very consistent cleaning services and local contacts for any issues with the house, and were relatively cheap because they were typically able to fill these houses with weeklong rentals all summer.
With Airbnb and VRBO, sometimes they are just a marketplace for the exact same rental companies that already existed, under the same terms and conditions, but a higher nightly price, and sometimes they are far less professional operations, and it's not easy to tell which is which when you are initially paying.
Last summer we rented a house directly through a vacation rental company that was also listed on VRBO for a third of the nightly price it was listed on VRBO for. We're dreading the day when the only option left is VRBO.