Astronauts travel in space in command modules using rockets, which also carry payloads. The payloads are delivered in the relevant orbit, and the command module returns to earth, after the rocket stages are discarded. Why did we need the shuttle then?
A few of the goals of the shuttle, unattainable (at that time) by command pods are:
- Reusability, especially of the engines (the most expensive part of the rocket)
- Lower Gs reentry
- Bring back payloads from orbit
Capsules are small - one, two, then three people. Orion will seat four. The Starliner and Crew Dragon hope to seat seven.
The Orbiter seated eight, and at a pinch could seat eleven.
The STS had the ability to return it's payload in the event of most of the failure modes of traditional launch vehicles (unfortunately it introduced two new failure modes)
Crew and cargo launches are usually separate, not together. The Shuttle was an effort to cut costs and increase flexibility while reusing the launch vehicle, but due to a number of factors (such as an Air Force requirement for cross range) it failed.