I found a similar question on StackExchange with a good answer https://ham.stackexchange.com/questions/9098/what-are-the-technical-reasons-that-there-are-no-fm

I found a similar question on StackExchange with a good answer https://ham.stackexchange.com/questions/9098/what-are-the-technical-reasons-that-there-are-no-fm-transmissions-on-the-long-m https://ham.stackexchange.com/questions/9098/what-are-the-te...