My point (as another commenter pointed), was more that, as long as you do not put a lot of money in, you'll have ample opportunities to recover, even in the worst case. Especially in the market we are in. This does not invalid your point, as I agree that there is plenty of jobs and money to do around here in the sector.
Your point is valid if (and only if) your income stream from consulting or contracting can be scaled up and down fluidly enough to catch the ups and downs that your startup business generates.
Most enterprises/jobs prefer the 'surrender your soul' approach to hiring and contracting, partly to eliminate competition from current and former employees, partly because they prefer to get a stable stream of work from you.
Markets are fluid - that's what the word means. So just because the market is crazy for engineers right now, 2 years from now they could be begging on the streets. If you've been working on your own startup, and depleting any savings you have, the opportunity cost is going to be obvious to you.