Yes, owners can cancel rentals for all kinds of reasons. One simple reason is that they might unexpectedly need to use their car. HyreCar customer service is known for helping you find another rental so you can get in something right away.
HyreCar discourages car owners from cancelling with a policy that states after 3 cancelled bookings in a one-month period, all of their listings can be deactivated and their account can be suspended.