Exactly.
How many Enfields, K98s, M1 garands, 1903s, what have you, were cut down in sporterizations or bubbaizations (there is a difference), and are worth so much less than an unaltered version now? You're correct that they're dirt cheap now, and that it is hard to de-value a $75 rifle that goes bang. The problem is in 40 years, when your sporterized $75 rifle is still worth $75, and the one pulled out of the same crate by someone else is worth $750 because it was not cut up.
Certainly it is your property, and you can do with it what you want. Just realize that they are not making any more.
Mike