i think its b/c he is so mean nobody would marry him except a computer!

Wife is what the computer is called, it was said in an episode. It was Wired Integrated Female Encephlograph, or something like that. They aren't married.

Actually, the wife's name is Karen. Maybe it all started when Plankton tried to steal the krabby patty formula. When he was trying one of his bizarre schemes, he found a lone shrimp. He brought the shrimp home and raised her like his own daughter. But then, the shrimp soon became a prawn. She was too big to fit in the Chum Bucket, so Plankton sawwed her brain out and put it into a computer. Relieved that she was now a robot, the shrimp forced Plankton to marry her in celebration. She was tired of shrimp and wanted more connection with plankton after an experience in her life. Plankton knew he would be considered a freak if people knew he was married to a computer-prawn. So he simply called her his Wired Ingegrated Female Encephlograph or W.I.F.E. for short.

She a Wired Integrated Female Electroencephlograph

Nice Imaginaaaaaaaaaaaation, Sandy-ego303.

well mabe it is because he has no self confidence when it comes to women

its because no living person would be able to stand him so he married a machine

It makes the show more interesting, and it's exactly what Aladdin3 said above.

^I've wondered that myself. Wouldn't salt water ruin the wires and everything inside a computer? But it is just a cartoon...so in the world of SpongeBob, that doesn't matter.