It's the way I've always viewed it. You have frontline starships carrying out the fairly big missions with a number of rarely seen (if ever) support ships carrying out very routine logistical operations (personnel transfer, equipment and supply deliveries, etc.).
But in the more distant reaches of the Galaxy, you may see some of the frontline starships carrying out logistical support missions too (in both TOS and TNG, the Enterprise
was sometimes ferrying cargo and passengers to and from various locations).