Why people try to flag someone instead of outplaying?

Hi. In my last game my opponent had so much time on the clock while I had very little:
https://www.chess.com/game/live/99388925875

I seem to be always slower than my opponents and I noticed in this situation more people will try to flag you instead of just outplaying. He could have just taken his time from move 40 but instead he kept making one second moves. I'm happy to get the win but he would have won if he just used his time to out think me.

For people in my situation I recommend having premoves allowed in your settings, otherwise I would have lost. What's your opinion of why people flag? Just inpatience or they think this is more likely to get the win?

Play with increment.

If they already blundered something, it's their last hope. Also maybe, they once losed much games by time, and now they know that it doesn't matter how good you played, if you have low time on your clock.