Why is shift key the largest key on the keyboard?

Considering, the fact, that there are no standardizations of size for keys on keyboards; and, other factors, such as, its purpose, size, flavors, such as, mini, ergonomic, split key, rotatory, etcetera, etcetera, etcetera.

Its like saying: I have a car; and, assuming that, because it's a car, I have (4) doors, when I could have (2), and then ask what is the largest door?

Synopsis: Question is faulty

Recommendation: Rewording

Example:Generally, the largest key on the 101-key US traditional keyboard or the 104-key Windows keyboards is the shift key?