The release of iOS 10 didn’t exactly go smoothly.
Many iOS users found their devices bricked – after installing the update they were stuck asking to be connected to iTunes. iTunes would only replace the OS, wiping out all data on the device – and even that wouldn’t succeed.
If you only use an iPhone for phone calls and don’t use a lot of apps or media with it then you can probably skip this and throw caution to the wind. Otherwise it helps to be aware of best update practices and what they can and can’t protect you from.