The more time you spend riding the indoor trainer, the more likely you are to develop the habit of riding on the hoods. It's much more comfortable. You can see the TV better.
But there are several reasons why you need to ride in the drops while riding in a pack. Riding in the drops will improve your aerodynamics and allow you to get more benefit from drafting. But the bigger reason to ride low is to lower your center of gravity. This will make you MUCH more stable and give you much better control of your bike. You will negotiate corners better. Riding in the drops will also put your fingers closer to the brake levers, and give you better leverage when braking and allow you to push the bike forward when braking hard. Riding here will also prevent you from getting your bars hooked with the rider next to you.
Riding on the hoods is certainly more comfortable. You can breathe better. You can see the road better. It doesn't hurt your neck and back. But it's not giving you optimum control.
And if the riders around you want you to have anything, it's optimum control of your bike.