Federation allows charging so clubs are just obliging. If its within the rules why shouldn't clubs charge entry. Some clubs don't have a multimillionaire on the committee or a hundred sponsors. So basically a club has 9-11 guaranteed functions (home games) to make enough money to support the club that season. If they can get an extra function in through the hosting of a State Cup round well good luck to them. Its just the luck of the draw.
There will always be the people who refuse to pay the $2 to park inside the ground but drive to the front gate feigning ignorance, the people who bring there own food and drink to games. Support your club/suburb and get to the game regardless, pay the charge and buy something from the canteen and stop complaining.