There are obviously going to be exceptions. Every rules has that. Hear why I said “usually a sign” rather than “it’s a guarantee with out any exceptions”.
But to take your startup example, they generally short on base salary with the hope that you score big when the company sells / floats. Which is a very different scenario to saying “we aren’t going to pay you more because we are unprofitable”.
Also, if a regular (ie non-startup) business isn’t profitable and are then freezing wages as a result, then that’s another good indicator to update your CV. You might be lucky to get a decent severance package, but even if you do, you’ll still want that CV updated.
Take the startup situation:
We were unprofitable year 1, we were break even year 2. Year 3 we look to repay investors and begin fun times. Year 4, fun times.
I suppose I can think of enough exceptions that I reject the theory the original OP posted.