Well, coming from Sodexho, perhaps I can shed some light. I ran a food service operation that fed 650 people. Prior to that I was the Food Service Director for a unit that had 1100+ population. Prior to that, I was at a unit that did over 3000 transactions per day. All that said...
Of the units I visited or had responsibilities to, we had chefs (usually formally trained or long-time restaurant types) as well as Directors, Assistant Directors, Sous Chef, or some combination thereof. So I can't necessarily agree that there is nobody in charge that knows anything about food. For Sodexho, our on-going training was relentless and very market-driven. We would benchmark local specialty food stores, make trips to NYC to see what the offerings were in similair operations as well as sending much of our regional culinary staff to Hyde Park every few years. Not to mention our annual raises and bonuses were tied directly to customer/client satisfaction surveys.
Now, there are certainly some variables in cafeterias, as there are in restaurants, gas stations and grocery stores. If the unit happens to be a Profit & Loss account, it may be running extremely tight on portion control and labor, for example. If the unit is subsidized (like private corporate cafeterias) they may be a little more free wheeling with their dollars. Then there are the other places that fall somewhere in between. Hospitals for instance, may be self-op and running their own food service. In this case, the unit may be running under the direction (and guidelines) of the hopsital's nutritional services department. In this case, it may taste like, well, hospital food. In their defense, though, budgeting is always a concern. It is difficult to serve a nutritionally balanced meal with mass appeal for $.63 cost. Try it... it ain't that easy. There are some larger hospitals that have food service operations that rival some semi-decent restaurants, including in-house baking and wine lists. Don't laugh... I've seen it!
As for schools, well the same goes for them. I had the opportunity to open a school unit about 4 years ago. The staff, administration and students all had HUGE demands on the food program and were extremely vocal in their demands. As such, we had to tailor plans after plans after plans to satisfy everybody. When we were done, our program was instense! We had a round-the-clock production team, including a bake shop, catering operations teams and a legion of bus staff, servers, prep people and administration. The food was exceptional. Not because I was there (not trying to be conceited) but because the school had very deep pockets and the food program wasn't an afterthought, like it is in most cases. We had omelets-to-order every day, crepes 2 or 3 times a week, grilled steaks, a static and seasonal menu. As well as vegan, lacto-ovo vegeterian menu and 'regular' menu every day. That also included pizza (from scratch) to order, 1/2# burgers on homemade rolls and salads made of organic greens from a local farmer. That is one extreme. And certainly I have seen school lunch programs that squeak by on a shoe string. Serving the bare minimum because either nobody cares or nobody speaks up. Real trash food. Chicken nuggets 3 days per week. French bread pizza the other two. Served on flimsy paper plates by people that look like flimsy paper plates.
I am not sure if this answers your question any more than "why was dinner at Joe Shmoe's so bad?" I think cafeterias are just one other aspect of food service, like catering, fine dining, quick serve or take-out that needs to be examined in its own right. Money is normally a big player in corporate food, health care and school food service. Most places charge $3 or $4 for an entree, dessert and drink. Keeping in mind food cost is around 35-40% and labor is around 40%, that doesn't leave much for owners/stock holders/etc once all the non-controllables are pulled from the equation.
My 2 cents.