[EricH]

Originally Posted by iCurtis

I understand the reasoning about being able to turn them on and off, but the external tank falls away too, and the shuttle uses the Orbiter engines to change orbits, doesn't it?

I think that's why I find this so confusing is it seems very at odds with itself. Why would they use liquid fuels for launch (from the earth to LEO at any rate) if the SRBs work so well?

The main engines are ONLY used during launch. After launch, they shut down for the duration.

However, there are those two pods right above the three main engines. Those have smaller, liquid-fueled engines and are used for larger orbital maneuvers. There's a technical name for them, but I can't remember it offhand. There are also the various steering engines at various places around the shuttle.