You may never have encountered a cocksucker that truly loves sucking cock. They are out there, so don't give up hope.
However, if you are hung really thick, even the most dedicated cocksucker is going to have difficulty satisfying you as they need to have some room in their mouth to work with. If your dick is really stretching their mouth open, they have no space to swirl their tongues around in, it's hard to create suction and almost impossible to swallow your cock down into their throat. Basically, all they can do is bob up and down on the head and maybe an inch of shaft and give it a lick or two when they come up off it or just lick it like a lollipop or ice cream cone.
Not very likely to give a great orgasm, so if you're really thick, you may have to settle for getting good pussy and just enjoy their attempts to give you head as an appetizer.