These are two very different beasts with a small core component of similar functions/features.
LR excels at organization of collections and "developing" or "adjusting" of photos. Think of it more of the software version of a "dark room"
Photoshop is more of a photo manipulation and creation tool, giving you far more editing, compositing, and retouching tools. Try removing hairs, cleaning facial blemishing, or say reshaping an arm or leg in LR vs PS. There is a reason covers of magazines are referred to as being "photoshopped" and not "lightroomed"
I use both. I use LR to do a lot more of global corrections like color (ColorChecker Passport), white balance and applying these changes across all images in a shoot, as well as making some image by image adjustments, but when it comes to heavy lifting, correcting, and polishing of images, then the rest of my work is in PhotoShop.