I recently went camping in an area where there was no data reception. My iPhone 6+ still had 17% battery left after 5 days of using it like a normal phone (voice and SMS). Smartphones have short battery life because we do so much more with them. I'm sure those friends of yours could have made their phones last through to the end of the evening by switching off data once they hit 30% battery, but they preferred to have access to all that functionality that data provides, knowing there was a risk of running out of charge.

The point being, people have the power to make that choice with their current hardware, and they vote overwhelmingly to accept the lower battery life for higher functionality tradeoff.