Why doesn’t jQuery use $, and how can I get it do so (GLOBALLY)?

Why doesn’t jQuery default to the “$” when the script is added this
way?

The $ alias has been chosen by several different libraries an alias. This causes conflict if you try to use more than one library. It is a bit ridiculous, actually– like several major corporations all deciding to use the same phone number.

How can I make the $ use jQuery, globally, across my entire site?

WordPress load jQuery in noConflict mode to avoid the problems caused by the above foolish aliasing. You should not reintroduce those issues.