Bots are actually a great place to practice control of your own character. They're terrible opponents, but they allow you to learn how a champion works, and, ideally, how to use their kit properly. Obviously, when playing against players, you have to change because players don't play by the same rules, but it still lets you build a solid, basic understanding of the champion's design and purpose.
Otherwise, they're pointless. After learning the basic mechanics, you move to blind/unranked draft queues to learn vs players.
It still baffles me that people have memorized perfect micro against bots, and will play specific champions in bots to maximize that. There's no challenge in mastering a predictable AI's reactions and using them to get a high kill count.