Imagine you coming back to the game after 2 years to check your investment and all your airdropped SPS is gone. This is essentially "stealing" assets from inactive players, which IMO is a really bad and shady practice.
No, it's not "yours", there is no reason to keep the airdrop forever.
Just claim them to the respective accounts, no need to take them away.
There is a huge difference between two years and forever. If a game is good, then the players can return to it years, decades later. For example a few months ago I still played MS-DOS games released in the 1980s/1990s. I grew up with them in the 1990s, and in the early 2000s. Then I have not played most of them for years. Probably I will play them in the future too. One of my favorite video games is the Heroes of Might and Magic II (1996).