For email - most people use the official app and assume they have to use it. You sign up for Gmail, you get the Gmail app. You sign up for Outlook, you get the

For email - most people use the official app and assume they have to use it. You sign up for Gmail, you get the Gmail app. You sign up for Outlook, you get the Outlook app. 1 service = 1 app. For browser - on mobile most people use whatever the default browser on their device is. On desktop - Chrome. Pretty much everybody just downloads and uses Chrome.