As Steam's digital storefront has grown, an increasing number of games have been removed from sale on the platform. Often, this is the result of a game's publisher requesting the game be de-listed, whether due to license agreements expiring, the game receiving a remaster, or the game shutting down. However, Valve will sometimes go out of their way remove games from the Steam store, typically due to in-game content violating Steam's Terms of Service.
Although some games that are removed from Steam will return to the service, whether as re-release or a remaster, many never will. In the case a game is removed from Steam, previous owners will still be able to install the removed title and play it as normal, however players who have not already purchased the game by the time it leaves Steam will be unable to do so.
Typically, the store page associated with removed games redirect users back to the main Steam store page. However, some games (typically those removed to promote a remaster) will still have a store page, with the purchase button removed.
In the case of removed free-to-play titles, players can sometimes install them regardless of whether or not they played the game while it was available, through the use of Steam's "steam://install/" command.