I agree. The experimental nature of many Dreamcast games is a fascinating thing to look back on. Certainly, nobody else was doing anything like Seaman, as per your example. To those unaware, coming across bizarre games like that piques their interest in a "that was a thing?!" sort of way.
In addition, we all know that the very name "vaporwave" is derived from the term "vaporware," and while the Dreamcast itself isn't technically vaporware (real vaporware is never released at all, of course), I have to wonder if its lack of commercial success contributes to its popularity on the scene. Combined with the nostalgia of those who
did have a Dreamcast, there might be a sort of desire to share with the world what they missed out on (tying back to my point about people not knowing anything about the Dreamcast). Indeed, to this day I believe the Dreamcast was unfairly misaligned, and it's a shame that it's mostly known today as a failure.
Anyway, I also adore the look of Dreamcast games (and the Y2K aesthetic as a whole) and hope more creators explore it in the future.
View: https://youtu.be/n86xEwVdocc