Is it possible that you have kicad setup to use on demand github libs? (github plugin) And yes the default setup is to use these on demand libs.
Check it via the footprint library manager found in the preferences menu of the footprint editor or pcb_new.
If the libs are of plugin type GITHUB then you use on demand libs.
If this is the case then kicad will download a zip archive of the footprint libs every time it needs them. (The downloaded files only live for one session. So restarting kicad means you will need to download them again.)
This is one of the reasons why it has been decided not to use the github plugin in the future version 5 release. (It is not even the most important reason.)
I would suggest you setup local libs. Have a look at the FAQ for details about that: How can i install a specific version of the footprint library?