Concealed Armors is a mod that adds a category to armor pieces called Visibility but is also made for fallout 4. I don't know why there aren't more of these types of mods available, but it sure would make the game play more fun and realistic. If you are interested in using this type of armor, I suggest looking into a couple of different places to find them.

The first place to look for this type of armor pieces is fallout new Vegas. This category is created by Nisas, who is also the main developer for the fallout series. His website is also a great place to go if you want to get help on modding your fallout games. This is the one I was referring to when I said that there aren't as many of these types of modifications available for fallout 4 as there were for Vegas. But he does have a few, so I don't think it's a big concern.

The second place I would look for these types of mods would be inside of the master files of the game. This can be found at addressed folder. Inside of the addressed folders you will find all of the files associated with the armor categories you can use. I'm pretty sure that this is where you will find Concealed Armors. There isn't a picture credit for this mod yet, but I have seen pictures of it and they look pretty good. I'm assuming that the picture credit will be given to someone special though, like the lead designer.