Why not just make the option available?
If people want to use it, they will - and if they don't, they won't.
Simple as that, let the market sort it out for you. It costs nothing to accept and the effort required to begin using it is minimal these days. See how you like it, most people who try it tend to stick around.
As to why you'd want to hold Bitcoins.. well look at the price, enough said
