You don't spend two minutes on a tender. If your cruise ship is too big in a harbour for mooring and tenders are used to get people to land, you easily have a half an hour ride. If the cruise ship's engines crap out in the middle of the ocean, let's say 600 miles away from the nearest harbour, it will be 24 hours.
You need to fill the tenders to 160 people if you want to empty the ship. Otherwise you go 24 hours to the harbour with half the people, 24 hours back, then another 24 hours. You still have no luggage.
And the whole thing is not safe. It's safe enough if your ship is hit with disaster and you need to evacuate; 100 times better than the alternative (swimming away from the sinking cruise ship), but if you evacuate a ship, I would guarantee there are broken bones, possibly people killed; and they _don't_ have toilets.