They can take up a lot of space
Windows 10: How to Delete Temporary Files! [Permanent]
Windows 10 creates all sorts of temporary files as you use your computer. These can be anything from cached system and application data, error reports, update files, to browsing data. Temporary files not only help speed things up, but some also play a role in troubleshooting system-related issues.
However, most temporary file types hang around for a long time and can eventually take up a large portion of storage space. If you are always running out of free space, you should delete these files regularly.
You can delete temporary files on your Windows 10 computer using the Settings app, the Disk Cleanup utility, or File Explorer. Additionally, you can use a built-in feature called Storage Sense to automate the process.