I don't necessarily share this view, but I've heard it enough times to steelman it: It's about dignity. I don't want to feel like someone owns me or can tell me what to do just because they lose some pocket change in my direction. You know the notion of the "deserving poor" that deserves our aid and pity? There's a corresponding idea of a deserving customer. I'd do my best impression of a dog for you if you ask nicely, but if you offer me $100 for it then I'll be insulted. If you offer me $10000 I'll do it but I'll resent you for it.
I get the point, but I assume the people keeping the museum open at 2 AM for some rich dude are the same people who do exactly that kind of job in normal hours.
In other words, they are asked to do overtime. So, as long as they are getting adequately paid for that overtime and they are not forced to do so (but I assume you can always find at least two people out of 20 who could do that), I don't think it's a big deal.
A better comparison - you're a member of the https://en.wikipedia.org/wiki/Actors%27_Equity_Association, the part which you auditioned for says "dog", and the script & stage directions are within general AEA guidelines for animal parts.
I've only volunteered in museum work - but there are obvious social rules about interacting with wealthy benefactors, and I'd assume that any competent employer in this space is carefully screening for comfort and skill with those rules.
(BTW, "wealthy benefactor" is very much a pay-to-win system, with tier after tier of "just how many $thousands did you graciously gift us with this year?" reward levels.)
If someone is doing it because of the arm twisting done by the economy and personal financial circumstances then of course it will not land well. I will feel exploited.
On the other hand if I am coming from a place of joy to be an usher at an odd midnight hour to a more sic recital, where I am paid peanuts or nothing at all, but I get to see the show and participate in the collective enjoyment of wonder it would land very very differently.
People get paid to sell their organs to tread water, I doubt they feel happy about it.
Even if they aren’t doing it for free. It completely depends on the situation, and the pressure the employers apply to get people to accept. In an ideal wonderland, management would offer enough money so the workers find it worthwhile. In reality they often offer the bare minimum and apply as much hierarchical pressure as they can to get away with not offering anything at all. I’ve seen it countless times, and it goes something like: "You know I’ve been thinking about that promotion for you… You know what could really help? What about you give us some help next Wednesday night?"