Surprise! The Piranha Plant cleaned it with a liquid that, once touched, knocks you out! Therefore, no one can sit in it anymore, therefore, I buy a cheap inflatable throne from WAL-MART and sit in that.
Also, the other throne is currently burning in an incinerator.
not that it would make any difference of course, i already destroyed that throne and took its infinity stone for myself, so we might as well keep playing with this throne instead