When Star Trek: The Original Series debuted its second pilot in 1966, the sets looked brand new as did the uniforms. Essentially, it looked like a new show, which is what it was, but Robert Butler, the director for the original pilot, "The Cage" had a different idea in mind for Captain Kirk and his crew. Captains' Logs—The Unauthorized Complete Trek Voyages by Edward Gross and Mark A. Altman revealed comments Butler made in regards to the ship and the overall tone of the series.
According to Butler, he begged Gene Roddenberry to give the show a different look. He wanted the ship to be more worn, one that had been in space already twenty years, and he thought the captain should have been at the helm for many years, at least seven, instead of a relatively new captain.
"I remember to some extent begging Gene and company not to do a new show, a new world, a new bunch of costumes, a new craft. I begged him to do a timeworn craft that had been up there for twenty years, a captain who had been out there for seven, etc., and it all fell on deaf ears."Robert Butler
Obviously, Butler thought it would make a difference if the Enterprise had some miles on it and looked like it had been put through the wringer, so to speak. It sounds like, though, that would have put the crew aboard a ship that wasn't on top of its game, and with all the battles the Enterprise went through, how much could it have survived had it been that old?
Butler said he also had a conversation with Harve Bennett about Star Trek II: The Wrath of Khan. He hadn't been offered a job, and before anything could happen, he told Bennett that it wouldn't work anyway because he would want to "do it dirty" with "weathered uniforms." That sounds like the crew would have been in space for years upon years without any returns to Starfleet Headquarters or the ability to replicate new uniforms which would have made explaining how some other things were replicated more difficult.
Thankfully, the Enterprise and its crew weren't weatherbeaten and timeworn during the series or in the movies. Change isn't always good, and this is one instance, where I'm glad Roddenberry stood his ground.