Or not, if the needs of the plot outweigh the needs of the characters...
If you really look, however, what goes on in Old Trek is relatively well distributed. Everybody can shoot a phaser? Sure- everybody in the US armed forces gets weapon training, and a phaser is a lot simpler to fire accurately the a gun.
All branches use tricorders, all bridge officers learn to operate bridge systems...
But when Jerry-rigging a phaser or tricorders to do something other than its intended purpose, usually, its in the hands of a science officer or engineer...sometimes with help or tools from one of the other branches. Or a bystander.
That brings to mind the common "no skill roll needed for routine tasks; only roll when doing something unusual or difficult" mechanics. So you don't make a skill roll to use a tricorder to detect a mineral deposit. You do make one to jury-rig it into an emergency transporter beacon because you lost your communicator.