bots do run on hax except for the fact that when you have the hax on, the bots do also. They are called p0d bot. Of course, they don't come default with the hax, as you have to dl them seperate.
People play with bots with hax because the bots are programed with "way-points" in order to hide in the spots that normal players hide. The wall hack will then show you the normal places where people hide and where you can shoot through the wall. I am told this is a fairly common practice.
For example in DeDust2, the bombsite "B": There is a spot behind a box that you can shoot through the wall and hit an opponent if he is crossing. The hacks with bots will show you exactly where the best spot is. People usually do it as a clan, and without bots, to make the clan better (I know of a Cal I clan who does it. It is where I got the concept). I have no clan that would shut the server down to practice this stuff, because everyone would have to dl the hacks to practice and I know most people would not agree to this.
The hack dl'ed was as series or combination of hacks. It had the aimbot (which was never used because it is no fun), the wall hack (or a sort of wall hack where you can see the person threw the wall outlined in a colored box but you couldn't see "through" the wall.), and the speed (which was very funny to put it up to like 3x and shoot around).
Anyway, reason number one, the hacks allow you to see certain areas that you can shoot through walls for potential kills.
Reason number two: My friend and I would create a server and fill it with bots. He doesn't have the hack so I would put on speed and just goof around. Remember as I have speed, so do the bots (I don't know how it works, but it just does). He would have to kill like 16 bots goign 3x speed. It was fun.
Guess it wasn't worth it though, I never really got better, but it was fun.