Because they have 78% of the market share and Apple only has 19% of it? And yes competition is savior, imagine if Apple had any more share given how crappy the last iPhones are.
Apple takes in the lion share of the mobile profits. The rest including Samsung takes the scraps. Samsung is doing everything possible to copy the iPhone to increase their profits. Removing SD and removable battery are all part of a strategy to force users to buy higher storage capacity phones. In line with Apple, this is a move to increase profits.
Also, copying the UI and making the naming convention similar is a move to help scrupulous sales reps at various carrier stores sell iPhone like devices to uninformed buyers. Samsung will fail again and will be on their last leg this time next year.