If they don't do it, others will so they must do it in other to have their share of the market. I rode when they have 3 spd cassettes, then 5, then 6 and 7... after a while I got the current bike and it's 8spd (04 model) now most new bikes have 9spd.. and I am aware that they've already made 10 spd systems.

But I never seen a 4 speed, why?