Equivalent networking and social opportunities exist in plenty other areas of life that don't cost you tens or hundreds of thousands of dollars.
If going to college was truly not worth it, then you'd see a lot more people not doing it. The fact that going to college is a such a common course of action says that people actually find value in it (or there's a giant inefficiency in the market -- which is the argument of this article, but I think it's worth considering the alternative as well).
And I don't think the lottery analogy works. Regardless of what you (legally) do, you can't influence the chance that a single lottery ticket of yours wins. But you can improve the chance that certain low-probability events happen to you (like founding a successful startup) by your actions. And I think going to a good college can be one of those actions for many people.
Depending on your industry and (sometimes) on your college, you're more likely to get in touch with those more influential and powerful than you (for science it might be renowned researchers, for law high-up law offices, etc). Since your friends went through the same college experience, the same goes for them. Therefore you're all in a good position to help each other.
I personally want to go into biology-related research. College is pretty much vital for this since I have access to professors who can go beyond what's in the textbook as well as have numerous opportunities to work in actual labs.
Now, if I were to start a software startup I admit that college is not necessarily the best option. Teaching yourself is easier and more likely to give you a good-enough foundation and if you're in the right place it'll be easier to hang out with the right crowd. However, for people who otherwise live in places far-removed from tech hotspots, college can give them a chance to move somewhere with a better chance of being noticed.
Also, besides startup-related events, what other non-college ways are there to have access to lots of networking opportunities?