The old ticks vs parentheses issue: confused

Since being corrected many years ago, I switched from backticks to $() for command expansion. But I still prefer the backticks. It is fewer keystrokes and does not involve the Shift key. I understand that the parentheses are preferable because it is less prone to the errors that backticks is prone to, but what is the reason for the rule to *never* use backticks?