Looks like quite a few companies worked on the idea for orbital launches -- lift a rocket with a balloon and then launch from a high altitude.

Rocketry really isn't about height but speed. And balloons don't actually help so much with that. At least if you want to stay up there once the lift is gone.

Most of a rocket's weight is fuel. Ironically, most of that fuel is needed to lift the rest of the fuel from ground level to some altitude A, then the remaining fuel is used to get to A', and so on.

If you could first lift the rocket to a high altitude, you could get away with far less fuel. The smaller mass would mean faster acceleration (think a rocket fired from a jet fighter).

note: I'm not a rocket scientist or physicist :-)

There is a lot of talk about horizontal launch for spacecraft - I’m pretty sure steam catapults and aircraft designed to use them could change things as well.