I've said this before on a similar thread. I'm afraid it's the same old problem: location, location, location.
And, to a still quite significant degree, I think: history, history, history. PNE are 'storied'as people like to say these days; Argyle are just not. Generally long ago they may be, but compare their
honours to Argyle's - not to mention that they were one of the Football League's twelve founder members, and its inaugural winners, thus becoming the first national league champions anywhere and anywhen in the entire history of the infinite multiverse (as far as we know). I don't think the Devon Professional Bowl quite stacks up! (I watched two or three of those finals around the turn of the 60s/70s, along with maybe 1,000 fellow Home Park stalwarts - and I lived out in Yelverton, a two hour-plus round trip by bus and on foot.)
Like it or not, to most people in the country Plymouth the city, and Argyle the club, are in the backwaters. I think the only way this will ever change now is through promotion to the PL, and I for one, having wished for top flight football for Argyle all these years, am no longer sure if I even want that. (Well, OK, maybe just the one heroic relegation season during which they win everyone's hearts but just not quite enough points.)