Shift modifier is used for keyboard selection as well, and not just for single selection.
No matter where you are, no matter how long the list,
[Shift] + [END] selects everything from your current item focus to the end of the list,
[Shift] + [PgDwn] one page (however that is defined).
This also combines with the word jump of
Ctrl where appropriate.
i.a.W. Shift is a universal "selection extender" in keyboard navigation. It makes sense to extend it to mouse operations, too.
Arguably, it isn't ideal for mouse selection. However, there are other problems:
Drag&Drop is initiated by the same gesture. Mixing these functions in a single environment is problematic, especially since "accidental drag & srop" can be scary.
Scaling to scrolling lists works a bit better with shift: clikc the first element, use the scrollbar to navigate to the last element, shift+click the last element.
Scroll due to drag seems to be unsolved in the general case (scrolls either to slow or to fast in most applications).
Even when non-scrolling, in a large list, the Shift-Click seems slightly advantegous
Now, I agree this gesture is nicer than than shift click for a short, non-scrolling list. The downsides don't make up for it IMO.