@Patrick2364 I have also had many Superhost bonuses go to waste as I was not in a position to use them. You are correct that it's a feel-good thing that costs them nothing.
One thing you can do so they don't go to waste is to find another host who also has one they won't be able to use, and "book" each other's places for empty dates, even though you don't actually go stay there. That way you both end up with some $.
Or you could use it to just get away to somewhere close by for a night, but as a little break from your own environment. I almost did that this year, but never got it together.
To be fair, there are other companies which offer credits or gifts which do have an expiry date, as well.
Of course it would be great to be able to bank them, but that's not going to happen, because Superhost isn't really an acknowledgement of superior hosting, it's a behavior modification tactic to keep hosts stressed out, accepting all guests and kowtowing to the entitlement and demands of some of them.