Why is it necessary to have Plex Pass to be able to use Plex Media Player on the same PC as the PMS



I have a Plex Media Server on a Windows 10 PC for some time. I bought the app on iOS, I bought the app on Android (i think), I use Plex inside my home only but for some reason when I downloaded Plex Media Player on my Windows 10 PC (the same that holds the Plex Media Server) I was unable to play anything. It was asking me to activate Plex Media Pass. Is that normal? Can't I use Plex Media Player to play media from the same PC as the PMS without activating Plex Pass?

Thank you,