If my company wants more, they need to ask more. This then of course leads to a negotiation on salary and benefits from both sides. It's how the corporate world works.

If I have a side hustle, that is none of their business if I am completing the requisite work for my main employer.

I am sure that most of us could do a lot more for our employer. I could also clean toilets and clear snow for them. Shame on me for not doing that!

This is like you paying for a home builder to build you a house and then complaining that despite the fact that they did it within the agreed to budget and time line that they had extra time they could have been building you a nice shed as well.