I am a pilot and here is my experience:
A flight of 14 hours means that there are two full crews (for flights requiring two operating pilots). This usually means that the first 30 and last 45 minutes have all four pilots on the flight deck and during the remaining time, two of them are taking a break, splitting it up so that the operating crew—the ones at the controls for landing—get a long break around the middle of the flight, so as to be adequately rested for the arrival, but fully engaged with the last portion.
Many planes have rest areas; small rooms with a couple bunks and a couple seats. Sometimes these seats will have entertainment systems similar to those in the cabin. Other planes will have designated rest seats in the cabin; usually business/first-class seats with curtains to separate them from the light and some of the noise of the cabin.
With such a long flight, it would be unusual if some sleeping weren’t involved. Even if the flight left at body-clock 0800 and arrived at body-clock 2000, the flight crew has been in the plane since at least 0700, arriving at the airport likely 30 minutes earlier. With a close home or layover hotel, they might have awakened at 0530, but it’s likely earlier. That makes for a long, tiring day. Some sleeping is in order, but they can also pursue any other normal form of diversion available to the passengers: read, watch movies, eat, listen to music, play games, etc.
But come on! You have the chance to get paid to sleep! I nap aggressively, like lives depended on it.