Let's not ask the question why - with all the rock press and media support it had - there never was a punk or post-punk band (well, not quite true, if you consider Green Day post-punk they make the stadium grade) that could sell out a stadium in its heyday much less still fill decent-sized halls 20 or 30 years after its heyday.
Are "overwrought 70s arena rock fans" just more faithful or is it the staying and buying power of baby boomers who stuck with what they liked as teenagers? Is punk a music of the moment that needs to be delivered with contremporary urgency in a live setting, but doesn't "store" well or "last"? No market for a 5.1 remaster of Never Mind the Bollocks?
To run with your (poorly chosen) example, the Pistols did sell out arenas/stadiums on their Filthy Lucre (90s reunion) tour (e.g. here in TO). Granted that's not their 'heyday' but illustrates that their support is stronger than ever (or that their fanbase grew up, got jobs and exposed their youger siblings/friends to them). The reason that that they didn't do that volume in their heyday was their status as an underfunded, fringe group. The Clash sold out stadiums in their heyday for sure (well, maybe not stadiums, but playing Bonds for 2 months straight has got to count for something.... they did play actual US stadiums opening for The Who, and in Britain as headliners, dunno if they literally sold out those shows though).
The reason that there isn't a 5.1 remaster of Bollocks is because 5.1 remasters ARE bollocks. An actual Pistols fan wouldn't buy it (they'd download the original, or maybe even the remaster out of curiosity, or buy a used copy). .. though I'm sure I've seen a 180gr 'audiophile' vinyl (also [mostly/usually] bollocks FYI) reissue of the LP before (but they've done that for everything).
70s area rock was fuelled by this populist lets all be part of the group thing; peer pressure/belonging thing. The bands were (relatively) safe (with a few exceptions; KISS had a little bit of a hard time here and there due to the whole evil-looking thing, but nothing like that faced by the Pistols - banned from the radio and concert venues in England - even the Clash had shows cancelled by promoters just for the genre association) and so was the music. Punk was always meant to be the antithesis of arena rock, so I really don't get the point here. Not olny that but think of who was a music fan, demographically at that time. Boomers (tail end, but still). Punk just didn't have that potential fanbase size to work with; it took time for multiple generations to add up to that (but it has, and I dare say you'll find more Pistols fans int he world today than Deep Purple.... or at least Slade).
Green Day is not post punk. They started out as an relatively honest nth generation punk band and just got big (so get slagged by 'the real punks' - the Clash had that sort of asshat pegged on their debut record - that was one thing that was pretty new about punk: critisising/overtly mocking your audience - both Lydon and Strummer did a lot of that;, though obviously one was more mocking and one was more criticising/scolding). ... not that I am a fan, they have gotten a bit big for their britches and ego-overgrown (that rant by Billie Joe when their set got cut short at some festival recently was hilarious), but I wish them no particular ill will and just because I'm not that into them (I was earlier - a mix of their down to earthness then and my youth I imagine) don't mean they ain't punk (frankly, most things these days that aren't contrived pop sensations can be arguably considered punk on some level and anyone who argues that is forgetting what was important about that movement in the first place).