Question

Why does the President Pro Tempore usually preside over the Senate?

Answer 1

The answer would be the first option.

Early vice presidents took an active part in frequently ruling over proceedings of the body, with the president pro tempore only being called on in the vice president's nonattendance. In the 20th century, the role of the vice president changed into more of an executive branch position. At present day, the vice president is typically perceived as a vital part of a president's management and chairs over the Senate only on formal occasions or when a tie-breaking vote may be desirable.