Why do young earth creationists feel a young earth is essential for their beliefs?

nothing i read in the bible seems to imply what age the earth is, so why do early earth creationists insist on an early earth without biblical inference to its age (if there is could you provide it?) especially considering the overwhelming evidence that supports an earth millions of years old. early earth creationists like carl baugh who claim evidence (he is the one famous for claiming people and dinosaurs coexisted) has been exposed a fraud and a deciever by not just scientists, but other christians/theists know he is a fraud too.