I think it is okay for them to play on in a completely lost position. Someone with good technique shouldn't have any trouble converting quickly. If they just let their time drain, with no intention of playing on that is bad etiquette, and chess.com has a system to pair such players only with similar poor sports.
I am afraid converting is part of the game, and especially in lower rated games anything is possible in terms of stalemates and blunders, so playing on is perfectly justified.
Playing out 20-30 basically forced moves in a daily endgame over weeks, that is ridiculous. Nobody learns anything, it is a complete waste of time, and the losing party needs to resign.
That said, I do not recommend that a person resigns, until they can logically and in detail explain exactly why they are resigning.