> this model arguably makes even more sense for knowledge-economy companies that require little in the way of physical capital, and derive the majority of their value from the talents of skilled employees.Which is why you still have partnerships in business that are 100% service driven - consulting, law firms, etc. Software falls in between because it requires knowledge capital but it does produce something of substance that can be sold and re-sold.
Also, in partnerships you're sharing ownership because you bring something irreplaceable to the table (generally your personal relationships). Front-line developers are usually replaceable as much as they like to think they aren't. Yes, they're more expensive than a factory line worker and you can't just code 40 hours a week and churn out product like a factory worker but you're not irreplaceable. You'll find that the people who AREN'T irreplaceable, either because of some industry or domain knowledge, can usually demand increased equity or profit sharing.