...
If your work habits are pleasing to you and you can accomplish what you want w/o one, I'm not going to try to persuade you otherwise...
If, otoh, you're interested in purchasing lumber rough sawn and/or want to take on more or larger work and perhaps do some of the routine work more quickly, then a jointer may be of some advantage. However, you do decide on one, I would recommend that nothing less than an 8" one will satisfy for the long run unless small work is all you do, but even there being able to face joint something wider than 6" is a real benefit.
IMO, YMMV, $0.02, etc., ...