The problem isn't that there isn't a market. The problem is that it's a harder market. Shipping a hundred machines on a pallet to one technically-competent person is a lot easier than shipping out a hundred machines to a hundred idiots who then need support. So they're willing to take a slight hit (in Bitmain's case, it's what, 1% off the purchase price?) to sell to a few giants who won't ask a lot of questions rather than sell to a thousand idiots with a dozen questions each if you get the same amount of money from either group. Bitmain wants to maximise profits, and if you can get the same revenue while unloading 90% of your support staff salary your profits just went up.

If I knew that I was guaranteed to sell 1000 units, it'd be worth my time to R&D and manufacture a small miner. It's not that the dev and manufacturing costs aren't enough to recoup it. The logistics of mass shipping and customer support (which Bitmain has sucked at for years now, think how much worse it'd be with twice as many customers) is what makes it annoying. Actually, what I want to build I can pretty much guarantee will sell at least 1000 units; the only thing stopping me is access to chips.