I’m amazed how many people don’t use 3D Touch. Actually, no, I’m not surprised in the least. Apple offers no user interface clues for the user as to where 3D Touch can be used. Unless you’re willing to go through the entirety of iOS pressing hard down on everything, you’re not going to know where you can use it.
There are rumors that Apple might drop this feature from the new iPhones, and to be honest this might be a good thing. Not only is it something that people don’t use that much, apps that do make use of it hardly use it for anything all that amazing.