Amps are usually the first part to go in a powered subwoofer. Most companies know this, and it is often reflected in the warranties, with the amp going out of warranty first. (That is one of the reasons I like having
unpowered subwoofers.) If they used EQ in their amps, which is common in powered subwoofers, figuring out how to get it right would be troublesome. Most likely, the easiest way would be to use an ordinary amplifier (not built-in) and then use a microphone and something that analyzes the output and use an EQ for the bass. But the cost of that might make it less expensive to just buy another subwoofer. Not to mention the fact that some people are not up to doing that, and so they will just buy another subwoofer.
And yes, it is hard for a small business to survive. Given the current offerings, I would not want to try to compete at all in making subwoofers. SVS and Hsu would be hard to beat at their price points. This can explain why some small companies go for just the very high end, but that is hard due to there being relatively few customers who will buy such a subwoofer.