The vast majority of apps need to use the network, at least sometimes. Eg turning network on to download podcasts then off to listen to them is annoying.
Depends on what apps you are installing. I love denying access to the network for games. It removes almost all ads from them. Even beyond full deny access, NetGuard gives you a lot around the conditions in which an app can access the network. I'd prefer if I didn't have to do any of this and the OS was on my side though.
