Are you considering jobs that are extraordinarily demanding? What if you're an ER Doctor? Or an Air Traffic Controller? Or someone getting started in their career in their early 20s, when most of us possess the unique combination of a lack of life experience that would prevent exploitation and ambition? For these jobs, I can easily sympathize with the idea that after a workday they're too tired to develop personally. Moreover, it's a manager's job to sap every ounce of productivity out of a person. Modern technology increasingly makes this possible. Even seemingly mundane jobs like working in a call center can be so orchestrated that using the bathroom makes them fall behind. And productivity has done nothing but rise for decades!

I also don't see how your final paragraph really refutes rather than just restates their opinion. Hobbies produce projects and business ventures all the time. Someone also has to find some way or another to socialize with the community. Volunteering is a great way to do that.