I'm having a hard time addressing your concern, because your notion that it's harder for a developer to eventually become a director or VP than it is for a lawyer to become a partner is neither (a) supported with any evidence or (b) apparent from my experience.
I don't know anybody that you know who became rich, and so that whole second paragraph sails right past me. Especially when it concludes with a suggestion that hacker VPs are as rare as movie stars.
As for the partner track at law firms, uh, fine. Substitute MBA -> investment banker, or CPA -> CFO, or Med School -> Anesthesiologist, or any number of other careers that don't have partner tracks.
Even if your salary never breaks $110k as a dev, you're still fantastically lucky to get that in any career, and perfectly capable of becoming a millionaire. So, I guess, cry me a river about how hard it is for techs to succeed without starting entirely new businesses?
Finally, let me just leave you with an uncomfortable truth: it is a safe bet that you will never get rich starting a company, or any number of companies.
If your definition of rich is $110k salary or owning $1M in assets (which translates to relatively safe passive income of $40k before tax, according to the financial planning books I read) then sure, you can absolutely achieve it with careful career planning. I don't believe that's what most people would call "rich" though. There are actually people who will tell you that $100k in the Bay Area is "barely breaking it even" (not that I agree.)
I freely concede I could be wrong with respect to directors and partners. I work at a software company and my girlfriend works at a law firm.
I absolutely agree with you that the odds of getting rich by starting a company are low, all I'm saying they're better than the odds of getting rich by other means.