If there were no cars, just zero-G shafts and walkable corridors, the longest it would take you to get from anywhere to anywhere on the
Enterprise would be about 3 minutes, or 3 and a half at the outside.
There just aren't that many situations where that would be a problem. The bridge has remote stations tied into Engineering and Life Support, and if something urgent there has to be done in person, you can call over the intercom.
Eliminating the turbo cars would save on four things:
• The cost of building the ship is reduced.
• The turbo cars' energy needs are eliminated.
• The mass of the ship is reduced, saving fuel.
• Turbo system maintenance is eliminated.
I think all of that would outweigh the rare circumstance of a given person needing to race from Point A to Point B. And in-universe, it proves that artificial gravity is all or nothing ship-wide, making the elevator cars an expensive necessity.
OTOH, when you get to the
Enterprise-D, that thing is so ridiculously big, a case can be made for a system that beats walking even if zero-G shafts
were possible. It's bigger than many towns.