But this is where equity incentives serve to align these interests. If you develop a real killer app on your spare time, but integrated into your company's pro

But this is where equity incentives serve to align these interests. If you develop a real killer app on your spare time, but integrated into your company's product would significantly increase the valuation, retention, reduce churn, etc - then with equity (whatever the structure may be) you have an incentive to bring that work to the table. If it's pure cash, then your benefit is the same regardless of if you keep this work (done on your own time, on your own equipment, and off-site) or share it.