Most of these companies fly under the radar because they don't need media telling investors how good of an investment they are. That just invites competition.
I used to work at a company like that. Our competitor was all over tech crunch, etc but we were completely unknown to the tech community. We still beat them because we were focused on our audience which had nothing to do with the tech world.
I believe that the biggest exit ever, remains Microsoft. It is said to have produced more than 10,000 millionaires in 1986 dollars in addition to the handful of billionaires. Now technically, since it took $1,000,000 VC funding in 1981 [1], it doesn't meet your criteria. On the other hand, because it was a profitable company with a high pre-money valuation, the founders + Ballmer kept control. Because the valuation was high and the investment small, the VC had little effect on how the money was distributed.
I say this because, never taking VC is not a great long term business goal. Accepting outside investment is a business decision and one that in Microsoft's case probably helped all their employees and certainly did not hurt them.
There's probably a bias here around bootstrapped founders exiting at lower valuations because the take home of 100% of 10M is easier to get than 5% of 200M.
I made up the numbers here but I think many founders are happy to get that first or second base hit of change your life but not quite FU money safety net vs VC money forcing the bipolar choice between home run or strike out.
You've got enough to buy a house in SF, put your kids through college, and not have to work again, for let's say 50 years with a decent annual spend, if you put most of it into a retirement account.
If you don't count tech companies, plenty of non tech conglomerates, restaurants, even things like cosmetics and trading make it big on just their savings and bank loans.
One reason these are rare: if a bootstrapped company is valued at $100+ million, a small minority investment - say, 10% - is very meaningful cash for the company yet involves relatively little dilution and little or no loss of control. It gets a lot harder to justify not raising something.
(And yes, a bootstrapped business worth over $100MM is probably generating a meaningful profit, but the founders may not be comfortable reinvesting it.)
It also helps build relationships and align incentives with powerful firms that can be very useful in arranging an exit and getting the best price for it.
Microsoft took a small mezzanine round right before they went public. They didn't need the cash, but it brought investment bankers on board so that they had an incentive to get the best possible price in the IPO. Similar story with Whatsapp; they didn't need the cash, but having Sequoia on board gave them a stamp of approval that probably helped their negotiating leverage both in attracting employees and in selling to Facebook.
I used to work at a company like that. Our competitor was all over tech crunch, etc but we were completely unknown to the tech community. We still beat them because we were focused on our audience which had nothing to do with the tech world.