For how long?
We can't maintain zombie businesses on the basis that they might be permitted to reopen at some point next year or the year after.
They are only "zombie businesses" as they have been forcibly closed by government order and are either still closed by law or so heavily restricted by government covid guidelines and rules that they are temporarily unviable.
It would be grossly unfair to the business owners and staff if they were driven out of business directly due to government action.
Another important factor is that it's not just individual businesses that are at risk of failing but entire sectors of the economy - this is much harder to recover from (if recovery is possible) and much more damaging to the overall economy
In normal times if a company failed then other companies in the sector would have picked up the pieces and bough up the remains of the company or re-hired some of the staff. At the moment this isn't happening in some sectors as all the companies are fighting for their own survival. For example two of the UK's biggest Audio Visual production companies have recently failed and there is no sign of rescue for either