A lot of us never played the original Halo. Some people might be interested in it. I know I'm not, but plenty of others might be.
"The Quest for More Money"? You do realize that's why these companies make games, right? Money fuels the entire gaming industry - it sure as heck doesn't run on fan love. At the end of the day, you have programmers and bills to pay, and you can't pay them with fan appreciation emails.
If 343 studios wants to graphically upgrade Halo 1, so be it. It's their money, it's their time, why can't they make whatever they want? Even if you don't think it's a good idea, remember, they're not making the game with your money. They're making it with their own cash. So what's with the moral indignation? Doesn't a company have a moral right to make what they want?
Also, some people might have sold or lost their original Halo disc and might want to relive the campaign in HD.
Not being a big Halo fan myself (I only ever played Halo 3, and that's because it came with the 360), I'm not terribly interested in Halo 1. But I know others who would be very interested in it.
Also, they are working on Halo 4 now. That's gotta take up a lot of time and money. They probably don't have the resources to fully remake Halo 1.