At the beginning of a company, it's all hope anyway [1].
Investors are sophisticated enough to quickly reason about basic margin opportunity, and decide if the company could ever be profitable, even if the founders have no real business experience. The assumption is that by the second round or so, you can refine the estimate of "Could ever be profitable".
More importantly for venture capital, is that there are many profitable businesses in the world that have people with finance expertise. If you just wanted to invest in profitable companies, you wouldn't be doing venture capital. Instead, you're seeking companies that will have massive returns and become profitable some day.
If the founders still don't know how to do finance, but they're making a ton of money, you send them a CFO to tighten that up. Same way you send them names for VP of Sales, or whatever else they need.
Deciding to give up on a company that seems to be generating lots of money, and "just" needs to improve margins is hard. If you tighten too early, you've blunted growth. If you tighten too late, you've thrown away the money. For the last few years, the amount of money sloshing around meant you saw more of the latter. The firms "had" to keep investing their funds, so they were chasing more and more deals on hope. But $10M out of a $1B fund is still no big deal.
tl;dr: the rare thing is rocket ships, not financial sophistication.
[1] https://www.k9ventures.com/blog/2012/05/31/hope-and-numbers/