Why can't they program bots to jungle so you can practice your jungling?

I'm not sure if this is the appropriate forum (gameplay).

When trying out a new jungler, especially one that is technically difficult like a Graves (using his stacks takes time to learn well) or getting used to Diana's QR, it would be nice if you could have a fairly evenly matched game. If you play 5v5 (I usually play easy bots or 2 easy/2 intermediate vs 5 intermediate enemy when I'm learning a champion), you're left with a lane that is either empty, or 1v2.

Sometimes I'll play 5v4 with all easy and only 4 enemy bots, but it still doesn't work out well.

Also, what is the other game play with the plus sign mean?

Thanks for any help.