Imagine for a second that you become employee 10 in a new startup that you believe in. You dedicate it 15 hours a day for 5 years, everything went awesome, and now the company is worth 5B. Your stock options would be worth millions in case of a liquidity event. Great, right?
The thing is, it's 5 years later the company is probably 300-800 people now, and therefore is a very different company than the one you joined, and if it's still growing, it's be a different company still next year. But there's no liquidity event: You cant exercise your options because you can't pay the taxes. If you want to exercise anything, the company has to go public, and you sure don't control that. So you either wait in a job that probably doesn't fit you anymore, or your stock compensation was worth nothing. Therefore, whether the startup does great or not, you have to apply the 'I might want to quit' discount. If I am assuming 8 years to IPO, which is not insane that discount is going to be huge by itself. I'd not rate my chances of staying in a job for 8 years as 1/10. And that's without considering that, career wise, you'll be learning more changing jobs every couple of years or so.
Let's compare this to a public company: Their stock compensation has none of that complexity, especially now that RSUs are the way to go. You can sell them for cash immediately at the stock price that day. The downside is minimal, and chances are your first block of shares comes after one year, so if you hate your job, you sit there a year, sell your shares and quit.
Given how much stock the bigger companies are awarding developers, you have to completely ignore compensation to go to a tiny startup: You kind of have to bet in the world around you changing to make exercising options early to be more or less free, along with believing that the startup will go the distance. Those are odds I'd not take