Again, not all content comes merely from movies and TV. Games are a big thing, and if the next MS and Sony consoles (Nintendo is only just now catching up to / slightly passing the current gen with the Wii U) aren't capable of supporting (with enough graphics horsepower to actually use as opposed to 1080 resolutions now) 1080P/60 3D I would be disappointed.
Joe Six Pack may not connect his PC to his HDTV, but many many PC gamers can and do. Sometimes I play at 1600x1200 on my ye olde ViewSonic P-series 19" CRT monitor, sometimes I play at 1920x1080 on my 3D capable DLP (though I haven't gotten around to playing with iz3D and such to play in 3D from the PC ... I have played in 3D from the Xbox). I just have to change the input select on my HDMI switcher, and load the game up on the other "monitor" that is now attached to my computer. (USB keyboard / mouse and extension / hub + Monoprice HDMI extender PID 8008 ftw - I was using a 35' cable before but it started flaking out, too much getting moved around with hooking / unhooking PC)
Are PC gamers enough to justify the creation of such a standard? No, not really, not if that is all there would ever be. But it wouldn't be. Consoles would pick it up, and even if that alone isn't good enough, it's good enough with both of them to wedge the door open wide enough for it to eventually become mainstream. Consumer 3D recording devices are only just now becoming available to the masses (i.e. 3D camera phones), it's only a matter of time before people take having a 3D 60fps camera phone for granted. And at that point, even if mainstream movies still aren't shot in higher framerates, there will still be a call for support of higher framerates for all the non movie / TV stuff out there.