If you add the capability to do it then I can give you a thousand reasons why someone should need it. They could be photosensitive and need to avoid sunlight, or agoraphobic, or have children they can't leave home alone, or follow a religion that requires them not to look upon an uncovered woman who is not their wife. They could be poor and unable to afford the travel, or live far away from the meeting place.
By the time I'm done listing reasons, there won't be anybody left without one.
The same is true for parking spaces, but giving everyone the closest parking space is not an option. How is allowing anyone to attend remotely not an option?
It is not an absolute formula. You have to use judgement, and sometimes you are going to get it wrong on the boundaries.
You define reasonable by using reason. You examine the situation and try to see if you can make an accommodation for the person that lets them do their job while not sacrificing performance. If you can, you do it.
You justify making these accommodations because you realize that there are some people who have conditions that make following the same routines that most people do impossible. We also realize that if you let everyone have those accommodations, it will not be sustainable, so you grant special rights to certain people based on this.
The handicap parking is a perfect example. Or pre-boarding flights for people in wheelchairs. Obviously you can't give everyone handicap parking, because that is the same as giving no one handicap parking. Some people can't travel as far, so we let them get the spots up front.
Same with pre-boarding. If everyone pre-boarded, it would just be boarding. But we also know that some groups need more time and space to board, like people in wheelchairs. So we let them board early.
I never understand this attitude that we aren't allowed to accommodate people who have hardships because it is unfair on people without those hardships. Like, what? The unfair part is that they HAVE the handicap in the first place, we are just trying to make it a little more fair.
Life isn't fair, so we make laws that are a little unfair in the opposite direction to try to even it out.