That's because the syntax was redesigned to be more orthogonal. So $ is always followed by a word to expand a variable and not an arcane symbol, % is used for a

That's because the syntax was redesigned to be more orthogonal. So $ is always followed by a word to expand a variable and not an arcane symbol, % is used for a wide variety of ways to get process ID's, and it's easy to set up arrays besides just $argv (plus if you do $argv on its own, it creates one word for every item in the array, without you having to worry about bizarre quoting). Most of these differences, and why they were made, are explained in the manual.