what are the common things you need a microsoft account for?

1. you dont need a microsoft account to update 10, yes?

2. what are the common things you need a microsoft account for?

A Microsoft account is not needed to update.
For a major hardware change it's a safety or backup plan to have a Microsoft account:
https://support.microsoft.com/en-us/...ardware-change

Microsoft account is used to buy and install software from the Windows store.

It is used to sync settings between devices that all use the same account. Which is pretty useful.

You can use a numeric pin or Windows Hello with a compatible camera to log into your device with a Microsoft account.