1. Lennie is dependent on George because he is so slow. The guy can't even remember anything for more than a couple seconds! Living all alone smack dab in the middle of the Great Depression would just be impossible for him. He can't think for himself, he can't make normal conversation, he can't even handle a mouse without killing it! Without George, Lennie would be doomed. Plus, I think Lennie likes George. Even if he could live on his own, I don't think he would.
2. I think that the reason George does not abandon Lennie is because he kind of feels sorry for him. He's seen the Lennie can't handle himself out there, and doesn't want him to get hurt. He may be a bit of a jerk, but he's not heartless. It looks like they have a bit of a history together, so that may also play a part in it. George may not even be planning to stick around with Lennie forever. He may just be trying to find a good place for him before he sets out on his own.
