I’d say design for maximum given market . The LIRR will never order M series cars with R160 bench seating because they will never carry enough passengers to warrant it, and the service they’re providing.
Same applies to airlines. Ryanair will pack 737-800s with 189 seats, but Emirates would never think of putting 440 seats on a 77W, given the long-haul market those planes serve.
In the case of buses, well, depends on what your route is. High density, high frequency, still crowded, cull seats. Otherwise, keep.