First, rather than look at these necessary accomodations as something workers shouldn't get, you should look at it as a very useful bit of flexibility that all workers should receive.
You are thinking about this from a single perspective, but it is a massively complicated & interconnected issue.
For one other perspective, consider what would happen is companies didn't do what you call "subsidizing". Effected employees can't then keep their job, they have to take leave or find another job all together. That's bad for the company which loses experienced employees and must now pay to identify, recruit, and train a new person, who doesn't know as much about how things run in that business. That person is going to be much less efficient for 6-months to 1-year before they are completely comfortable. You are then subsidizing them instead.
Or consider a broader economic perspective: Let's imagine companies say they won't subsidize like this and impacted people have to take a 10% pay cut. Over 60% of the workforce in the US is white collar, jobs more likely to be WFH possible. That works out to about 79,000,000 workers. Average salary for White Collar jobs is $60,000. Let's say 1/3 need to work from home for family reasons, and they all take a 10% pay cut. That means the economy loses $158 Billion dollars. That is nearly 1% of our GDP, just in that one move, and it doesn't end there: Those people cut back spending. Areas heavy with such workers, like major cities, SV, etc., suddenly have a huge % of their customer base that has to cut back spending. Businesses like restaurants etc., already hurting, take another hit because 1/3 of 60% of all workers (works out to about 18% of the total workforce) now has to cut back discretionary spending. Even if that accounts for only half their 10% pay cut, that's equivalent to almost a 10% reduction in customer base.
Or consider it from a healthcare standpoint: Putting additional stress on this portion of the workforce will have significantly higher stress if "unsubsidized". That translates to more mental health problems, and expensive health care. Some of these workers may lose their insurance if they drop to part-time work, putting an even high burden on the the healthcare system.
Small things can have massive ripple effects. Saying "It's not fair!" is mostly not a helpful guide to resolving complex issues. Right now solutions are needed to keep society running while we get out of this crisis. Approaching it from a narrow sense of fairness is short sited. It won't be fair to the local shops that lose another chunk of their business. It won't be fair to other workers who have to pickup the slack left by a lost employees. If you're going to bring "fair" into things, you can't cherry pick only the one thing. That is one-dimensional thinking. You need to think multi dimensional. You need to consider second and third order effects.