There's various reasons a primitive might become less talkative than before, or even go away from Skins's island altogether.
The sparkling old dude, for example, who hasn't been around much the past few months.
There's two reasons the sparkling old dude isn't seen much any more--he's dealing with some, uh, marital problems because he's an old guy married to a much younger woman; he doesn't have the vigor to please her any more, and so she's turned to the horsey Mrs. Tutweiler down the street for those needs.
And he finally realizes he's been had, by Skins and the professional Democrats and liberals; at one time, he actually thought his opinions and his feelings were important to them, but over time it sank in that no, they aren't; in fact, professional Democrats and liberals probably laugh more at the primitives than we do.
The subway cat, for another example, appears to have been more or less permanently sequestered in a big building with small rooms and soft walls, where access to the internet isn't possible. Her loving caring sisters had the guts to do what the subway cat's mother always wanted to do, but couldn't get herself to do it.
The bobbolink primitive, for a third example, apparently was a mole created by a graduate student wishing to measure attitudes about poverty and homeless; the study done, the mole was euthanized.
The convenience store primitive, the locust primitive, and Dennis the Menace seem to have learned what Great Damage loose lips causes, and so they've reined in themselves, although one wishes they hadn't.
The list goes on and on.....