A majority of my locomotives I own are not in Like-New condition, and that's likely because most of them I bought used.
I know there are a some people want their trains to be as in nice, original condition as possible, and are rather nitpicky if they aren't.
I was going over my Vision Line 700E Hudson I purchased 4 years ago tonight, and it (whether it was its original owner or not) has plenty of paint scratches on the undercarriage area, has a slightly (but not badly) bent classification light, and a few rub marks on the boiler. But I've done some touch ups to make those defects much less noticeable, from painting over the scuffs and marks and what not. Regardless, this engine is still my most favorite in my collection.
Now I know that the engine goes down if there are any touch ups, but from my point of view, especially with these modern era trains which end up devaluing over time anyways, these engines are for me to care for once they're in my possession. It's kind of like owning a car. To me, it's better to get things fixed up than leave it looking all scratched. But there's another reason. I kind of feel caring for these trains in my own way adds to the value of it myself personally, similar to weathering a train or adopting a poor animal who needs help as my pet. I don't know, that's just my opinion.