They haven't. Gear and items always get replaced by better gear in mmo type games, BUT you can still buy gear made from 10 years ago. WoW for example: -Has access to all previous instances, raids and dungeons. No lockouts. The que lets you pick from a list. If you want to play 10 year old content you can. They also have reworked all the old instances content to work with current que protocols. - Legacy vendors for gear no longer accessible from the current gear vendors. - all pvp battlegrounds are available. - expansions don't overwrite existing content and make it accessible. If the zone has a new quest line in it's area, they use a technique called phasing to not let you see it. While other people are playing the new content 5 feet from you. They figured this out when Cataclysm released. That's just a few examples of how WoW has not compromised your old purchases in any way. -