If you don’t care if you have anyone in your lab, and you don’t have any expenses, you’re pretty free as a tenured faculty. But if you want students, you need

If you don’t care if you have anyone in your lab, and you don’t have any expenses, you’re pretty free as a tenured faculty. But if you want students, you need to find grants for them. And if you need materials/travel/services/etc for your research that’ll require grants too.