I think the issue would be that it's a fantastic way to drive away attendances down.
If anyone was considering whether to travel to Barnsley for example, spending £100 on a day out and then saw that actually about 200 fans are going up the Jazz to watch in a warm bar with beer flowing, they'd choose that.
It would have a direct negative impact on attendances I think.
I would assume if it made economical sense the club would probably already be doing it but it feels a shame they don't put up a big screen (a la Brentford away in 2002) charge, say, £5 to get in then people can also drink in the stands when the game is on to top up the club profits. Could have the fosters backpack guys filling up your beer while you sit and watch the game.