The issue is that many of these companies have never demonstrated that if they want to they can be profitable. The big assumption in these growth models is that there is a point where you can just magically flip that profit switch.

For example if I run a lemonade stand where I spend $3 to make a $1 glass of lemonade, even if I am able to use investor capital to keep growing my lemonade stand to be the only lemonade stand in town, or even the world, it's not clear that I can survive if I'm forced to make a profit.