Well most people decide which sub to buy by first researching which one would perform the best
Yes, but some people are better at researching than others, and some people refuse to buy a subwoofer that they cannot hear before buying (which means they won't consider an internet direct brand, at least not new; some people will not consider used either). They also buy based on price, so what people buy need not be what they think is best and wish they could afford. Very few people really buy what they consider to be the best subwoofer made, at least among people with good sense who cannot afford to spend thousands on subwoofers.