What Happens When Companies Stop Being Profitable? Do Shareholders Just Jump Ship?

Public companies are always chasing profits, we know this. It's not always possible to be profitable, however. So when there profits dry up, is it an automatic death sentence? Or how does it work?

What brought this to my mind is seeing how many retailers and grocery stores have disappeared and how little variety and competition there now is in the US' "free market". When household names vanish, diminishing ROI for shareholders seems to always be the reason why.

If shareholders are so vested in the profitability of companies, why do they not do more to ensure their survival and continued prosperity?

I understand if these are stupid questions and I'll get lost if you tell me to...