Because someone who cares might buy the brand and do something good with it and be a competitor. ID Software is still a strong brand, and it the hands of another gaming studio it might pose a threat.
1. Tax write off.
2. Acquiring a competitor, and then closing them down is a way to decrease competiton.
Serious question, is there any kind of entities that can be owned, but not "dismantled", if you don't want it you need to try to sell or make it independant.
Would there be any chance to make it a thing when a company is bought?
There's also the case where new teams can self organize to form new studios in the aftermath. That's also a factor on whether it makes sense to pay for the previous name or game license, or simply start over.
You can also make all sort of post acquisition agreements.
These usually take the form of making stock available at steep discounts in response to actions e.g. in the event of a 20% layoff any employee from the time of acquisition can purchase stock at $0.10 a share, any one laid off will get a million dollars severance, if acquirer shuts down the studio the original founders have the right to re-acquire all IP and trademarks for $1 -- those sorts of things.
This isn't a specific kind of entity, any business entity can have Shareholder Rights Agreements. It's a bit of a game to get the terms right so everything is in good faith and agreeable.