I understand people think that makes it easier, because “90%” of the world uses them…but 99% of my paying customers are in the US. I will do my best to make sure metric works, always have even before you could buy a single thing from me. I am located int the US and buy bulk hardware in the US, Metric is significantly more expensive. So If I make it all metric only, I instantly raise my costs which passes along to the customers that choose to support me.
I made a machine from day 1 that supported metric and imperial fasteners. This gets brought up so often you would think I made it not support metric, it always, always has. I chose #6 machine screws so M3.5 would work, The whole system is based off M8 bolts that fit the bearings perfectly, in the US we use a substandard fitting 5/16".
Number one complaint. M3.5 are non standard, too hard to get. Odd, I can get those in all the same places that carry metric fasteners in the US. Nothing I can do will be perfect, people will always complain on such a giant project.