(I am not trying to be snarky. What's your definition of bootstrapping?)
It's not entirely clear to me how Microsoft was financed, but there was absolutely outside financing (August Capital: http://en.wikipedia.org/wiki/David_Marquardt ). Also, Bill Gates was born pretty rich. "His father was a prominent lawyer, and his mother served on the board of directors for First Interstate BancSystem and the United Way. Gates's maternal grandfather was JW Maxwell, a national bank president." (from https://en.wikipedia.org/wiki/Bill_Gates). I'd wager his folks were angel investors in one form or another.
A business needs to make money as soon as it can. It's how it survives. Facebook and Twitter are exceptions.
Example: Say Amazon was bootstrapped. They couldn't have run profit-free for years like they did. The result of bootstrapping Amazon? Higher prices. Slow hiring. No marketing. Little-to-no cash for R&D. Maybe company-death because they couldn't afford to wait for the market to catch up with their vision. Or maybe a faster-moving competitor now has room to move in and take the leadership role.
Do you think Amazon made the wrong choice to raise money, assuming Bezos' wish was a combination of impact-on-the-world and wealth?
As for bootstrapping: sadly, lots of young and inexperienced entrepreneurs underestimate how much money they'll need to execute. That's not a control issue; that's a starting-a-business-when-you-have-no-business-starting-a-business issue.
Finally, the word "big" is too subjective to have any real meaning here. If you told a group of first-time entrepreneurs that they could own 100% of a highly-profitable multi-million dollar a year business, most would probably tell you that's "big enough." And even though many of them fly under the radar, there are a countless number of those businesses in and out of the tech world.