We no longer build as much, we assemble, which is a good thing. Many thanks to the various vendors who can supply us with electronics, artwork, kits, etc which make the dream of owning an arcade a reality. If you are just coming onto the scene now, you have a whole plethora of options and may not even find this site. If you do find this site, you may not post your build since it breaks no new ground.
Pre-built is now an option. You can go with an Arcade1up or a variety of other manufacturers and ikea style build a machine. Without getting into an argument on how close it is to the real thing, I believe it scratches the itch enough for many folks so their dreams of a real arcade in their house is accomplished from a trip or two to Wal-mart.
The environment has changed. Like Soul Asylum said, nothing attracts a crowd like a crowd, and a crowd we don't have.
Bottom line, just like real arcades, the niche community we have has it's heyday behind it. It's not a good or bad thing, it's just a thing.