You'd have to ask them. I am unaware of any valid poll ever conducted on the matter.

Though lacking data, I personally am convinced that so few people run a node (I assume you mean a fully-validating, non-mining wallet?) because they have no incentive to do so.

I run a fully-validating, non-mining wallet because I value the ability to transact directly onchain. I guess most Bitcoiners don't give a shit about the ability to do so.

Then again, maybe more people that we have thought realize the falseness of the dogma that such non-mining, fully-validating wallets provide some sort of benefit to the network itself.