It's really a matter of personality. Startups are high risk, high return. Big companies are moderate risk, moderate return.
A startup is all about risk and low return for employees. You get paid less, work more, and have less job security and benefits.
A big company will give you a noce salary, benefits, and better job security without the risk. It might also give you stock options that are worth something and can sold.
If you were employee #1000 in Facebook, you'd make $20M.
If you were employee #100 in Dropbox, you'd make $10M.
Source: https://genius.com/Sam-altman-lecture-1-how-to-start-a-start...
These numbers are all calculated back in 2014, and they're probably a lot higher now.
Also, personality. Some people don't enjoy job security and want a little adventure. For those who have to do it, they just have to do it. It's similar to the pioneers from colonist era Europe going off into strange countries.
Most exits would be less than Dropbox ($10B). Say it's 10% of it, a $1B exit, which is extremely respectable. But as employee 100, you get $1Million. That probably requires 4 years at the company to fully vest. Assuming you were paid $150k/year, your total compensation is $1.6Million (pre-tax). Assuming you spent the same time at FB, you can probably pull in an average of $300k per year, depending on which level you start at [0]. So your best alternate path has a return of $1.2million.
You beat the FB route if you are the first 100 employees, vest most or all of your shares, and your company exits at $1B and above. I'm not sure what chance of that happening is, but it's probably lower than 75%, so the expected value of the startup route as an employee is lower than $1.2Million. Of course, FB route doesn't have a 100% chance of happening either, but it's a lot closer to 100% than the startup route.
[0]: https://www.levels.fyi/ - I used the average of E4 average and E5 average.
But there are cases where it has paid off to be a lowly startup employee. For example google itself.
Or you can be employee #100 in a fairly large startup like Dropbox, Zooplus, Booking.com.
There's easily around 50,000 of those roles open, including places like India and China.. So I'd say the odds are one in 120k, if you were born as a random human.
But if you are a software developer in the top 10% globally, you'd be one of 2 million. Let's assume only 25% of these jobs are tech.
That puts the odds around 1 in 160. If you're in a tech city, it's even higher. It's not great, but not terrible either.
My ratio of multimillionaire startup friends are a lot higher than 1/160, but I'm pretty sure it's survival bias, because the people who have succeeded are the ones most active in the community.