I can't see the sense, under normal conditions, in drawing out a game that is clearly lost. People who play on in this manner do so out of spite or ignorance.
If out of spite, however much merited by an opponent's comments or conduct, the 'gains' to the loser in terms of satisfaction are pretty small. I speak of what I know
Early on in here, I made the error in a pair of 7/14 tournament games of suggesting my opponent resign two utterly hopeless positions. My motives were rational; my suggestion politely put - we were holding up tournament progress; and surely we could both be doing better things. To no avail. I received no reply. But my opponent then dawdled his way to the bitter end several weeks later. I've learned to keep my mouth shut after that!
Far more common is an absence of resignation due to ignorance. This probably stems from lack of familiarity with, or concern for, basic chess etiquette. I find weaker players rarely resign. One only need scan the final positions on the RHP homepage to see that some guys will play on long after the farm's been sold and the wife's run off with the bank manager
A resignation avoids unnecessary humiliation - it's an act of courage, even dignity, but never cowardice.
So when the game's up, resign and move on. Life's too short to t*t about making gestures, or hoping that some miracle will rescue you. If the other guy's good enough to be well ahead, he's good enough to finish the job. Proof won't alter that