Very true, the dremel spins upward of 20,000rpm at it highest setting, whereas a cordless drill is maybe 3000. There are a few accessories for the Dremel that would work in a drill (wire brushes or sanding drums come to mind), but most of them need to turn faster.
Not sure what sorts of crafts you do, but I can say that the Dremel isn't very useful for most DIY work around the house. They advertise it that way, but don't be misled. For every use the Dremel has, there is a better way to do it or a better tool to get it done. I use mine on rare occasion for cutting bolts shorter, cutting the edges off of plastic electrical plates, or polishing small pieces...But I can say that I have never used it for any serious DIY remodeling applications.
For DIY/remodeling use, give the variable speed RotoZip a good look. They can use 1/4" or 1/8" (dremel) bits, but also have the guts for use as a mini-router, cutoff tool, drywall/backerboard/wood cutout tool, etc. You can get a kit with a good assortment of attachments for around $100, and can buy a few RotoZip and Dremel bits to suit your needs. Coupled with your drill, this would be much more useful and versatile. I really get a lot of use out of mine. Right now it is caked in sheetrock dust.