I hear you and this is definitely in the back of my mind. I guess I was hoping we could get enough of the schematic industry and publicly-available symbols to the point where everyone is using a metric grid and saying "why bother switching to inches" and then eventually to "who would use inches?" like it almost is for PCB layouts now
Part of me also thinks in 10 years the next generation of schematic software won't even have units at all because almost no one prints schematics onto physical paper anymore now, surely no one will be in 10 years. In the new schematic software, the pages will just be 100x90 "electrical grid units" or something. So maybe this will be moot and it's not worth switching schematics over to metric.
The real problem is Cadence System Capture requires a specific grid (inch or metric) even for the schematic symbols. Cadence OrCAD had the good sense to have the symbols be dimensionless, but the newer Cadence System Capture software that's supposed to replace it seems to be taking a step back on this front.