You can sharpen a carbide scraper with a diamond whetstone and a little lubricant, but it is slow going and you have to be very careful to maintain the edge geometry. Carbon steel scrapers are much, much easier to sharpen.
But you can do some things with a carbide scraper that would be really tough to do with a steel scraper. I recently had to clean up some aluminum gasket mating surfaces where someone at some point had beat on the edge with a hammer, so there were raised bumps in the gasket surfaces. I was able to pare down the high spots with a carbide scraper, by laying it completely flat on an undamaged portion and then, keeping it flat, sliding it over to a bump and taking off tiny shavings until the bump was gone. This worked really well, and would've been really tough to do with a carbon steel scraper.
I've come to think of my carbon steel scrapers as more of a rough tool, and then I finish up the tricky spots (like around bolt holes) with the carbide scraper laid flat and used with a shearing motion.