Because you're very likely to find someone prepared to pay twice as much (or more). That person might even be you.
And as time passes, the differential will most likely get bigger, not smaller.
Opinion? Yes, I suppose, but one based on how vintage & rare values have routinely moved over time. Not just in basses, but in pretty much every collectable.
And yes, a 1953 would be worth double what a 1963 would cost you. Broadly speaking.