You’re not “wasting” them if you just don’t need the extra bits, Are you wasting a 32-bit integer if your program only ever counts up to 1000000?
Even so when you do start to need them, you can gradually make the other bits available in the form of more octets. Like you can just define it as a.b.c.d.e = 0.a.b.c.d.e = 0.0.a.b.c.d.e = 0.0.0.a.b.c.d.e
Recall that IPv6 came out just a year before the Nintendo 64
If you’re worried about wasting registers it makes even less sense to switch from a 32-bit addressing space to a 128-bit one in one go.
Anyway, your explanation is a perfect example of “second system effect” at work. You get all caught up in the mistakes of the first system, in casu the lack of addressing bits, and then you go all out to correct those mistakes for your second system, giving it all the bits humanity could ever need before the heat death of the universe, while ignoring the real world implications of your choices. And now you are surprised that nobody wants to use your 128-bit abomination.