You know, I think profit does drive designers, but profit isn't always within mass-market parameters, if you know what I mean. Would Smythe make more money if they offered plus-size jackets? I don't know; Suz did a rundown on what that would mean in turns of tailoring and fit model costs, etc., and it would obviously cost a fair bit of money and time -- something a smaller label like Smythe just may not be able to accommodate. Possibly they have found the sweet spot for money in/money out and expanding into other realms would tax their resources without returns.
As for men, I do believe men's clothing is more flexible and forgiving in terms of body shapes. I have yet to meet any man who frets about being an hourglass, pear, apple, triangle, or rectangle. They don't have as wide a variable in hips and hips to shoulders, plus they don't have the same variation in garments that have to work together. Yes, some are taller, some are finer-boned, some are fatter, some are slimmer, but the basic body shape just doesn't change that much.
Also, there is also a much bigger tradition of bespoke for a truly lovely men's suit for those rich enough to afford them. Plus - when's the last time you saw a suit sale without free tailoring?!
I'm sorry to hear the anger and frustration from larger women about labels not designing for them. If it helps, most designers don't seem to be designing for me, either, seeing how many clothing items out there I find hideous and/or ill-fitting.