Modern keyboards are based on those created for typewriters, and while they have several digital-specific innovations like the delete key, they also include many quirks and symbols that date from the era when typewriters were the primary means of official communication.
The “shift” key has not changed much from its original function, but it’s interesting to note that it does go back to the original typewriter layouts. There, it actually mechanically shifted the actuation created by pressing down on a key, to an adjacent set of type arms. So although we think of it now as “shifting” between lowercase and uppercase letters, or numbers to symbols, it did have its origin in an actual, physical shift.