The big VCs typically will expect extreme growth, because the big wins are needed to make up for the losses they will incur on many of the their other portfolio companies. That said, there are smaller VCs and private equity firms who will be happy to fund companies with lesser aspirations. Just don't expect comparably big valuations and you'll likely need to cede more control for less money.

"do they really expect this all the time"

This is an interesting question. I don't know if they believe but they def want to believe because without unicorns, they won't survive as most startups fail or have mediocre returns which is not enough for VCs to justify to their own investors/LPs.