Originally Posted by kitten_Val
But I know some people have, say, 5 totally different bits they are using depending on day/mood. So I wonder what's the reason for that.
I'm partially guilty of that. Most of my bits are basically the same in regards to shank length and leverage, but the mouths are shaped differently and I have different diameters. I have a thin sweetwater mouth, a thicker sweetwater mouth, a low port and a high port, all with virtually identical shanks on them. Then, I have one with shorter shanks and a ported myler/billy allen type mouth. Which one I use depends on what I plan to do that day and whichever one the horse seems to like better.
Sometimes I just use a different bit than they are used to to get them used to using different types of bits. When they go home, it is unlikely that their owners will have the same bits that I do so they need to learn to just accept whatever I put on them.