Cats like high ground.

My mother used to have a paper bag on the floor that the cat liked to go into. Once she bought a fancy paper bag that had pretty cloth on the outside but was still crinkly inside (found it at a novelty store, I guess; she likes to shop). Put it down on the exact same spot. Nothing more than a disdainful sniff. So, yeah, cats are kind of evil that way.

Picky or just following the dictates of his nature?

I'm not sure that the notions of "picky" and "[any given cat's] nature" are as opposed as your phrasing seems to suggest.

Higher is safer. If he does sleep on the floor somewhere else in your house, he must perceive that to be a safer place than the kitchen.

Also, yummy kitchen smells go up.

It might be colder on the floor. And the vantage point from the chair is better.

I think it's deborah here that has helpfully referred in the past to "Rule #1" for understanding cats.

Rule #1: Cats are weird.

I'm sure it makes sense to the cat, not just a quirk. They generally don't like to lie on the floor unless there's a sun spot or they feel like they won't be stepped on. One of their hunting strategies is to wait in a high place and watch animal traffic below, so maybe it relates to that. But it could just be Rule #1.

I agree...I bet he likes to sleep high up. So does Citizen Cat.

Of these reasons, it's probably the height thing. Trilby doesn't tend to lie on the floor, although he does like to sit or lie on the heating vents. He likes to sleep on chairs, tables, my bed, my computer desk, the ironing board, etc.

Put a heating pad in the bed and he won't care where it is.

Any cat over 8 years old gets a heating pad. There was a UN resolution to this effect.

Heating pad? Wouldn't it have to be kept plugged in all the time?