Even within successful companies, it is a challenging task to figure out just how much value each employee produces. Some positions are required, but do not produce revenue. Sometimes whole departments are a sunk cost.
It is up to each employee at review time, to argue that the value they produce is far greater than their salary; in order to negotiate a raise. No one is automatically entitled to anything extra, just because the company had a good year.
If I charge a client $50k for some software and they made $1 million profit from it, good for them? As long as they pay our mutually agreed upon rate on time and there was no hostile negotiation, why should I feel suddenly entitled to more money if that wasn't in our contract? How do I know how much of the value is from my work and not their marketing or idea?
What you're saying seems as crazy as me saying that someone who bought my software for $99 and used it on a multi-million dollar project is being unethical unless they give me more money. How on Earth does that make sense? Should I be forced to switch to a royalty model? What if I make more selling copies at a flat rate, what if I don't want to have to investigate the finances of thousands of customers and have to deal with that whole trouble?
For me it's the same thing regardless of whether I'm selling my labour or a product. I can choose whether to accept a flat hourly rate, equity, or a mix of both, and usually the better deal is the hourly rate.
If I find a way to hire a software engineer for market rates (say, $200k/year in the US) and get $2M revenue from their work, good? They can ask for a raise or a bonus, we can renegotiate, they can leave if they're unhappy, but I'm not obligated to give them more money than was in our agreement anymore than they're obligated to give me their salary back in the project fails.