I don't think "no thought process" is fair. Take "Amok Time" where at the beginning McCoy is leaving some room at the end of Spock's corridor which usually is a turbolift (with red doors). For this particular scene the door color changed to grey.
Which of the turbolift sets was "wild" and detached for interior shoots? Would the corridor doors have been removed as part of the process of moving the turbolift around, and replaced by whatever was the most conveniently available afterwards?