Professors typically have their own salaries covered, but need to secure funding for each new student they take on, so providing funding to an academic lab allows them to take on more students and grow (it’s not always the case that everyone is taking on as many students as they can manage). Additionally, it’s often hard for professors to get funding for non-student expenses (compute, engineering help, data labeling contractors, etc) through NSF grants and similar, which are often restricted to students.
Professors typically have their own salaries covered, but need to secure funding for each new student they take on, so providing funding to an academic lab allows them to take on more students and grow (it’s not always the case that everyone is taking on as many students as they can manage). Additionally, it’s often hard for professors to get funding for non-student expenses (compute, engineering help, data labeling contractors, etc) through NSF grants and similar, which are often restricted to students.