Why do dogs beg cats don't?

I have many cats rescued over the past 30 years that actually do. I just lost one (he was 17) that just loved to beg. He not only begged, the day before he died, he was still grabbing food off my fork with his paw. (and it was asparagus, at that!) If I came into the living room with a plate, he get on the back of the couch and try to grab off my fork as I ate (and at times I would, of course, let him). I have another older one that will literally balance up on her hind legs and wait for me to show her what she's getting when the can gets opened. She also loves to beg for pieces of roast beef, turkey or chicken.