Main approach to this problem in industry is when you approach cellular limit, you optimize.
I also agree that it is big engineering investment sometimes. But the problem is you are targeting low hanging fruit (stripping comments from localization, stripping symbols, optimizing images etc) or stuff that doesn't effect download size ( deduplicate files )
Those fixes are good for small startups, which you are giving away for free.
The main engineering problem for big companies is binary size, optimizations like "reordering of the build optimization passes" etc.
I would buy this as a tool, but as a service it is a hard sell for me.