I think the major difference is that in each of the fields you quoted, they only place to actually learn the skill is in the university classroom. The knowledge being passed on is hidden and selective. The same is not true with computer science. (Interesting though, that with things such as MIT Open Course Ware we may see this change in the future)
More and more, a college degree has gone from being a symbol of educational merit to being a caveat against absolute stupidity. It's lost all its original meaning.
I often see university being quoted as "showing that you can finish something/work hard to achieve a goal". Often, this line is spouted by those whose only achievement in life is that degree. It's simply not an accurate measure of anything, but it's the only thing in that a person in that position can relate to.
As somebody that spent my early 20's slogging through mud and being responsible for the lives of 8 men while surrounded by explosives and live ordinance, I personally find the argument that I didn't drink like a fish and attend a few classes hungover and therefore don't have a commitment to finishing what I started insulting.