That's one sorry reason if I ever saw one. It would work for the DKCTV's version of the King, given his bumbling behavior in that, but in the games, I don't know. There just has to be some reason behind it.
So, having played Donkey Kong Country Returns (spoilers will follow)...
Yeah, I know you're not in the game. Shut up.
Like I said, having played Donkey Kong Country Returns, the ape's hoard of prized bananas doesn't get stolen by King K. Rool this time, but by a bunch of thieving, sentient instruments known as the Tiki Tak Tribe. These dudes hypnotize DK Isle's wildlife, to which the critters take off with the bananas. Diddy flips and gives chase, and DK fails to get hypnotized because he's either too smart or too dumb. I'll take either explanation, to be honest.
It was later revealed that the Tikis were using DK's bananas to create an army of Tiki drones. So presumably, the bananas must have some sort of magic power. And that's probably why King K. Rool stole them in the first game, too.
But why does he hate them later on, I hear you ask? Like I said earlier on, in DK: Jungle Climber, the Kremling King says: 'Oh, sweet potassium-rich irony! I hate bananas anyway!' So why did he suddenly decide that he hates bananas, then?
In Donkey Kong Country 3: Dixie Kong's Double Trouble!, one would find the locked up Queen Banana Bird, after freeing her children and acquiring a so-called Gyrocopter. She says; 'K. Rool will never be able to look at a banana ever again!' Thus, Dixie and Kiddy managed to free her and she punishes the fiend by dropping an eggshell on him. Wut. It was probably a magic eggshell, so it counts.
But really, if you are being chased and punished by giant, sentient, god-like potassium-poultry, you'd hate bananas, too.
And that's probably also why K. Rool didn't appear in Donkey Kong Country Returns.