Guild Wars 2

Is there a specific reason these items are gone or were they meant to be limited time like some other cosmetics?

Basic Marketing.

When you see an item in the gemstore that is always there, there’s less incentive to buy it right away. You can wait until your next paycheck or grind out enough gold in game to convert to gems to buy it. In other words, you can buy it when it’s most convenient or on a whim, and so sales tend to be low for those kind of items after they are introduced.

However, when you see an item that’s only there for a limited time, if you want that item you need to shell out the money to get it asap, or you’ll never get it. Thus, these items tend to have significantly higher sales, even though they’re only available temporarily.