Don't all industries work this way? Construction has "old work" and "new work" versions of many parts. For instance, replacing windows on a finished house is a different job from installing windows on a house that's still under construction, so they build "replacement windows" and "new windows." We don't demolish functional homes unless they are unsalvageable; we cut into drywall and patch over the hole. The drywall would look bad if you looked at the backside of it, but the homeowners can't see the inside of the drywall and don't care.
This is a good analogy! Another similar analogy would be construction codes for earthquake proof, or fire proof or whatever safety feature new building must have to be compliant. We don't go and fix everything currently built unless we have to, or can.
The risk is of course, an earthquake where it could destroy all houses built before year X.
But we do the same in all industries, path of least resistance.