I wanted to step back a bit and discuss the reasons that people attend college and relate that back to Bostonian's original point and other comments in this thread.

1. Learning: Students attend college to learn. Sometimes it is general learning through a liberal arts education, and other times it is more career focused like with engineering.
2. Credentialing: Students attend college to earn a degree, as this is very often a requirement for employment.
3. Prestige effects: Many students choose colleges based upon the prestige effects which make them more employable. Note that this is slightly different from selecting a college for the prestige aura it gives the students, although many consider that as well.
4. Networking opportunities: This relates to the effectiveness of the alumni network. This can be separate from prestige effects in that some places like Texas A&M have extremely helpful alumni despite not being among the most selective colleges.

On the flip side, as has already been pointed out, colleges look for students that will make an impact at college while attending, make an impact in the world after they graduate, and and ideally donate generously to the college.

So getting back to Bostonian's original point, some places like MIT have decided that the Learning part is not something that they need to protect, and they started OpenCourseWare almost 20 years ago and if Wikipedia is correct, over 2400 courses are online. I think this works for most classes except special cases like Math 55.

But I also contend that's really not what people clamoring for free college want. At a minimum they also want Credentialing. But not all credentialing is the same. For example it is easy to get admitted to Harvard, take classes taught by Harvard professors and eventually earn a degree. The caveat is that this is Harvard Extension School, not Harvard College.

And of course Harvard Extension School doesn't have the prestige effects or networking opportunities of Harvard College or its peers.

To further crucify Wren's analogy, I contend that MIT Courseware is like the free veggies: high quality and good for you, and fortunately free. Harvard Extension and its equivalents are the mealworms, and Harvard College and its peers are Japanese Waygu.