Some apps have a legitimate reason for access to certain parts of your device (i.e., access to storage to save files the app has produced, access to location for apps that use that function - such as Google maps when you click to centre on your location). A few app developers even say why they need such access. However, in my experience, the vast majority just say they want access and don't say why, which IMO is crap of them. The worst, IMO, is when they give you the option to allow them to update the app in the future without asking you again. That's when they can (legitimately because you've given consent) access whatever the hell they like.