Tony Hawk Pro Skater HD will not remain on Steam for long, due to an expiring license forcing Activision to pull the game in the very near future. That means if you want to own the 2012 skating remaster of the original game and several of the levels from the sequels, you'll need to buy it soon or risk missing out on it for good.
Although music licensing hasn't been cited as the reason for the game being pulled, as PCGamesN highlights, this is almost always the case with older games and especially those like skating titles which traditionally feature a lot of licensed music from bands of the release era.
The date when Tony Hawk Pro Skater HD is set to be delisted from Steam for good, is July 17, so you have less than a week to buy it if you want to hang on to it. Currently priced at just $2, it's a bit of a steal, especially if you were ever a fan of the original trilogy of Tony Hawk games.
There's also a non-discounted DLC pack known as the Revert Pack, which gives you additional levels, a few additional skaters to play as and new combos you can hit.
Anyone who does buy the game will continue to be able to play it following its removal from the Steam store and there shouldn't be any issues with lack of support or online features like leaderboards. Online gameplay however was limited with this release to console versions, so there won't be much in the way of online components to maintain post withdrawal from the Steam store.