The point of admissions has become to determine that admitting a given student will do one of three things: Benefit the school through future press from stand-outs, alumni donations, and better GPA, SAT, and ACT stats in the various rankings (all leading to more enrollment in the future), benefit the school by paying to attend and not really affecting rankings, or whether they can pay and not really hurt ranks that badly.
And the number of free admissions to most areas of undergraduate study is 0. Full-ride scholarships are usually athletic, not scholastic, but most partial scholarships are based on test scores and apply regardless of the course of study.
>Also, couldn't we set the number of (free) admissions to certain areas of study based on the national need for those professions?
Philosophically, American universities are meant to 1) search for truth, 2) produce graduates who are educated about the most important findings and methods of the search for truth, 3) contribute to the general or local welfare in the process. Suggest to them that they are workforce training systems and you'll have a mess on your hands [0].
The private ones were doing this among the elite for hundreds of years, the public ones were meant to let the masses join the elite's party. Aside from specifically designed trade schools, neither are intended as (nor do they think of themselves as) servants of business needs for specific kinds of labor. That is why you see people required to take all kinds of "unnecessary" subjects like chemistry, physics, math, art, literature, philosophy, social sciences, etc. and even specialize in those things, regardless of whether they are relevant to career ambitions. And why this proposal is not tenable in the current system.
Part of doing this for the masses is being unselective. If public universities became more selective to decrease their dropout rates, it would be seen as a betrayal of their identities and the very purpose of public education. (For some reason people are a lot more tolerant of their children washing out then of their children getting rejected).
At the time, teenage/minimum wage was high enough in real terms were high and tuition was low enough (partly because public institutions had lower overhead, partly they had a lot more taxpayer support) that this was economically tenable. White collar employers found that college students were useful enough to put to work, even though their curriculum wasn't really designed at the employers' direction.
Even in computing. A philosophically pure Computer Science curriculum (and mine comes close) asks the question, "So we have this model of computation, and these machines that implement it. What does that mean? What can we do with it?" It does not ask the question "How do we best prepare workers for the IT departments of the big local employers?"
And this is why you get students learning things like theory of computation, fundamental algorithms, functional programming, operating systems, compilers, programming language theory and design, networking in the general rather than Cisco sense, etc. - things that re meant to be fundamental and timeless - instead of How To Contribute To Local BigCos Java/Win32 Codebases Right Now.
Maybe we've outlived the usefulness of this notion. It's less present in Europe, but in Germany at least the college liberal arts curriculum is simply shifted into high school and reserved for the academically inclined (Gymansium). It's not that they don't do it, they just do it differently.
Also, couldn't we set the number of (free) admissions to certain areas of study based on the national need for those professions?