like... No one's thought to put Seat Belts on the Bridge Chairs in All These Years?
Well, yes and no. The armrests acted as restraints when folded inward on the refit Enterprise
. Then in the Nemesis deleted scenes, we see that Picard's new command chair has a harness restraint.
EDIT: Forgot the Excelsior
from Star Trek III also had armrests that acted as restraints.