Yes they are used for motion capture animation. There is a lot more work post motion capture to get an animation going such as creating a character, rigging it, baking the animation to the rig, importing into UE4, using persona to create your animation graphs and finally matinee to bring it all together. There are also more advanced topics in all of the stages I just mentioned. Suffice to say just having a motion capture suit is not the key to creating amazing cut scenes, it is but one of the many tools/skills required.