Evidently, many believe that setting a time control is just a generic indication on the maximum duration of the game.
Yet it is repeated and explained in every possible and imaginable way... When choosing a certain time control, the aim of the game is to give checkmate within that well-determined time. So time management is an essential part of the game as well as moves, tactics etc. There's no point in reaching a totally winning position if you haven't spared the time necessary to checkmate. It's not that hard to understand.
If you don't like it, you have to play with very slow time controls. Complaining is futile.
Time is not the only reason why people don't resign. We are all humans and occasionally make mistakes, so I usually play on, there is that chance that the opponent may blunder and remove his winning position.
This even happens in daily games, I experienced this 2 times. I blundered and lost material in both games, but the opponent later on hung the rook, removing my losing position.