Why Did Microsoft Disable System Restore?

Microsoft hasn’t really explained why it’s not enabling System Restore by default. However, we do have some idea. System Restore can use quite a bit of disk space when it creates those snapshots, and Microsoft is trying to get Windows 10’s disk space requirements down. Microsoft wants Windows 10 to run on devices with as little as 16 GB of internal storage — all the better to compete with Chromebooks and cheap Android tablets.
System Restore is also less necessary thanks to other features in Windows 10 that can quickly get your Windows system back to a fresh state without a full reinstallation of Windows. Windows 10’s PC reset feature that will give you a fresh Windows system without necessarily wiping your files is one big help here.