Obviously you don't have to use any of those features, they won't slow your app down just by being available (maybe a tiny overhead in distributed code size, but meh).

- auto updates : primarily useful for commercial software that isn't "eligible" for, or chooses not to pay to use, commercial app stores. Or other apps that for whatever reason don't meet the criteria for public repositories and don't want the hassle (for the publisher or consumer) of using a private repo.

- Windows installers : same reasoning as above.

- Notifications : I believe its a standardised cross-platform api onto the existing system-specific notification apis, not a new notification system.