They actually DO save time by skipping the non-essential part of a map, assuming you are talking about the non-instanced part of a mission/strike. When you are vastly overpowered compared to the trash mobs in the region, unless you need to kill them in hopes of getting ammo reloads before advancing or are working on specific bounties to kill certain mob types, speed runs of missions/strikes will generally net you more runs in a play session. For people playing with limited amounts of time each day, it is crucial to get the most bang for your buck, so hammering out a bunch in quick succession will net you more, potentially, than if you sat and farmed all the mobs slowly and only got a couple of runs in. Don't mistake this as a defense for whether this practice is good/bad, it is what works for them. I've done it a few times when I had a small window of time to play, and have had a few times I was forced to do it or be left in the dust due to my fireteam doing it. I think the problem with random fireteams and this issue specific is the inability to communicate with them directly, short of creating a Party chat. If you were able to talk with your teammates and thus better understand their driving factors for why they are doing what they are, you may not be so quick to write everyone off as toolbags for running ahead because they only have 1 hr to play the game that day while you can play for 5-6 hours at your leisure. The converse of this issue are the freeloaders, those who sit at the spawn area of a strike and do not advance, while the other two advance, and get rewarded when they beat it. Honestly, I'd be more upset with a freeloader than someone who was willing to push the engagement, as long as the person pushing was doing so intelligently and for good reason. I'll take a random runner over a random freeloader, because at least the one is trying to contribute to the team, even if it may not be in a manner you prefer.