The majority of PIN2DMD colour artists stem from the vpin community, myself included, and I believe for a long time we didn't have the ability to run colour projects for large DMDs on vpins (though this is now no longer the case) and for a long time the Sega games didn't get any real love. I personally have a hardware 128x32 PIN2DMD on my desktop I use for development, and this means I don't have a practical way to test projects larger than that - I believe many of the other artists are in the same position.
Another factor (I think) is simply the increase in the number of dots to be coloured - that's a genuine concern, the more dots there are, the longer it takes to colour each frame! But there have been lots of tweaks and additions to the editor in the past couple of years, including some changes to the fill tool that would make it much more practical, as well as the increase in palette size which makes dynamic (ColorMask) scenes much easier in terms of managing your colours - this includes the main score screen alluded to a few posts ago, I bet it isn't as difficult as Sudsy thinks any more
Stick at it for a bit Soulrider911 - it's a long slog for sure, you can expect several months of a few hours per day, but if you're willing to put the work in it's very rewarding seeing your work on screen, and even more so when other owners reach out to ask for or compliment your work. There are lots of tips and tricks and threads full of advice on the vpuniverse.com forums if you are serious about it, but make sure you are comfortable with what's in store before you go that far - keep trying and see how you feel, and let us know how you get on!