Is Big 4 sustainable?

Two years ago, sustainability was one of the 'nice to have' issues and dealt mostly with ecology/green/nature questions.

Nowadays, the concept of sustainability appeared to me from other perspective, so vital and important - GOING CONCERN.

This, Going Concern thing became real and tangible during the crisis. The question is not - whether my company will survive. Sure, none of the Big 4 will not die during the crisis, but what will happen with your department, your salary, your role & tasks, your job, as these thing have significant influence on your quality/way if life? Theses are sides of the going concern concept,

I've never thought about....
...now, I have started thinking about it, and came across the list of The Global 100 Most Sustainable Corporations.
The Big 4 is not within that list. I believe - it's a sign, which shouldn't be ignored.