Well, keeping owls as "pets" is completely illegal, to start with.
I've done a fair amount of wildlife rehab, including at a raptor-specific center, and I regularly handle glove-trained owls.
Some of these owls do like to be petted, others are just waiting for the chance to claw your eyeballs right out of your face.
Owls really need whole animals in their diet, or they will become malnourished. We also use Bird of Prey meat, which is largely composed of ground horse. Chunks of beef or chicken are not sufficient to keep these birds healthy. For a small owl, like a screech owl, 1 mouse daily is pretty typical. Larger owls, like barn owls, will need multiple mice or a rat or two, depending on the prey's size.
And they have a charming habit of occasionally eating only the head off the mouse.
Pellets aren't that bad to clean up, once they dry. Many facilities will keep them to sell to schools for dissecting. Their droppings, however, are pretty heinous.
They're very cute but they really should never be kept as pets. It's heartbreaking how often people try to keep wildlife as pets, only to finally bring them to a rehab clinic once their malnutrition begins to obviously manifest, and they have to be put down, or are unreleasable.