Absolutely. I worked at ten, with employee numbers from single digits up to about fifty. As we all know, most startups fail. Even among those that succeed, few employees avoid all of the traps that founders and VCs create for them (e.g. dilution and special share classes) to get more than a modest payout at the exit. For most, even that "big payout" might not match the year-after-year premium they could have gotten by working and climbing the ladder at one of the already-big tech companies.
As one point of evidence, my two semi-successful exits did help me retire earlier and in more comfort than I otherwise might have. I'm grateful for that. OTOH, my three and a half undistinguished years at Facebook helped more.
Depends what you want. I had a guy work for us at my first startup: he was employee #6 and once we got to about 13 or 15 he decided it was time to move on. I was surprised, but he felt the business was just too big for him. And indeed I've looked at his career over the ensuing years and he's worked for some amazing companies...always just for a year or so and always when they were very tiny. Sometimes I noticed he'd worked with the same people, so he wasn't leaving because he was a poor performer (we missed him) but simply because that's what he liked.