and the more folders you index, the more windows resources you use up, which will slow your PC
indexing is a left over stupid "feature" from old , slow systems which were too slow to do real time searches as needed.
e.g. do you really need the content of internet explorer's history files indexed? - windows thinks you do - by default.
searchindexer is a huge resource hog. open task manager and watch, next time you start windows.
if your system drive is an SSD, then having windows build and constantly maintain an index for it was a waste of time, & will shorten your drives lifespan with endless scans for changes.
& finally, microsoft largely broke search in file explorer for many users ,with recent windows 10 updates, & have not bothered to fix it yet.
see here for how to reduce the impact:
https://windowsreport.com/fix-search-indexer-high-cpu/