I agree that it shouldn't matter who is on for what part. Everybody in this company - and everybody in any Broadway company, honestly - is fantastic, and I personally would never be disappointed to see an understudy. But just because that's how it should be doesn't mean that's how it is.
The fact of the matter is that there is a genuine concern that announcing when principals are out could affect ticket sales. These are a few of the sentiments I remember on social media when Taylor announced her vacation (and quickly deleted all mention of said vacation, oops):
- I'm so relieved I bought tickets for the next week when Taylor will be back.
- I was just about to buy tickets. Thank goodness I know this information first.
- Oh, I would love to see Becca/Jonalyn as Regina. Maybe I'll try to buy tickets for that week.
- Oh no, I'm seeing it that week for my birthday. I really wanted to see Taylor. Maybe I can ask for an exchange?
So yes, as silly as it may seem, this kind of thing does matter to ticket buyers. Whether the people who want to see the full principal cast cancel out with the people who want to see understudies on is debatable. Would I love to be able to plan in advance to see understudies? Of course. (I was indeed one of those people who bought a ticket during Taylor's vacation.) But I can understand why the box office doesn't want to reveal that information up front, and I'm okay with that. For now we either have to buy in advance and get whatever we get, or wait until the last moment and just hope there's rush seats left to see our faves.