Well, this doesn't surprise me one bit! As you said Doc, they've been doing this on every console. So why not take advantage of the Xbox Live Arcade as well and keep the status quo?
True, but it's the principle behind it all. Look what Konami has been doing, they've been using Digital Eclipse to redo the graphics and add true online play to these old games. It's more than just internet scoreboards, you've got co-op and versus modes too. Namco on the other hand has actually taken steps backwards. While other games on XBLA are offering a better-than-arcade experience, you can't even do local multiplayer in Pac-Man or Dig Dug. They're strictly single-player games with an internet scoring system. It all seems pretty shoddy to me, since I'd rather pay my measly five bucks to play an old game with a graphical overhaul and Xbox Live multiplayer with true HD support than an inferior version of an old arcade game for the same price.
I think they might be taking a step in the right direction with Pac-Man Championchip Edition, which got released today. I'm going to have to pick up the trial and give it a spin.