Let's ignore the complexities and focus on crude market value. A smart person with no college degree can probably earn $25,000 per year at 18. We're assuming a middle to upper-middle class background-- no special family connections-- and a reasonable work ethic. With a CS, math, or science degree from a good college, that jumps to about $80,000 at 22. That's a 34% annual growth rate in one's earning potential! (I'm ignoring the career prospects of Communications majors; a startup is much harder than getting 3.0+ in a CS program.) Typical income growth in the work world is 5-7% for average people and 10-20% (with ups and downs) for very ambitious people. I've been running at 17%/year since I left school, but that's likely to slow down as I trade off income acceleration for more interesting work and autonomy. My point is: being able to grow your earning potential at 34%/year, and probably have fun and learn a lot, while surrounded by intelligent people, over 4 years... is not something to walk away from.
Yes, everyone hates college sometimes. The lowest of the lows truly suck. Sleep deprivation. Drunk people. Final exam stress. Realizing that some idiots get in no matter how elite a college you attend. On the whole, though, if you struggle with college the problem is probably with you-- or more specifically, your level of maturity, and college is a great place to improve that.
Mark Zuckerberg could grow (in wealth and earning potential) much faster than 34%/year. College was slowing him down. Same with Bill Gates, Steve Jobs, etc. Most of us are not in that league-- not yet, anyway.
That's just discussing market value. Here's another factor. Forget about the startup dream and focus on the reality (for the middle 90%) of the work world. College is more fun, interesting, and educational than the first 5 years of the work world for most people. Don't throw that opportunity away lightly.