You've hit the nail on the head, and it points to what's actually driving it.
> It is medicalized... A day off work to rest, relax, and enjoy isn't just vacation (which also implies these concepts), but a mental health day.
The destruction of individual agency, in favor of top-down systems of control. The culture is a self-reinforcing thing, but what's pushing the culture is individuals having to express their own needs in terms of what the system will allow them. The "day off" isn't allowed - paid ones are not required to be provided by law, and the wealth-centralizing economic treadmill has made it so most people do not have the finances to lose a day of pay.
Similarly with emotional support animals. Airlines have policies that certain types of pets need to travel in the cold cargo hold, getting left waiting on a hot tarmac, with horror stories abounding. Landlords outright prohibit pets or put you over the barrel for "pet rent" (it's not like paying pet rent gets you extra space or amenities, or makes it so that chewing on the woodwork then becomes "normal wear and tear".
So enter people skirting their systems by any means possible, in this case the federal laws that created the legal concept of emotional support animals. And then comes the crab bucket mentality of rolling our eyes at people who we deem to be inappropriately using the escape hatch.
To avoid the euphemism/abstraction treadmill, we would need to be having these conversations maturely. But politics always seems to just end up going sideways (/me loosely gestures at the current ongoing destructionist catastrophe)
My thoughts went down a similar track as well. It is about justification. As collectivist attitudes increase socially, individuals feel the need to frame or justify and defend their individual actions and desires. Its not just that I want a vacation day and have leverage to take it (socially unacceptable), but I need it - it is necessary maintenance, but ultimately for the greater good. Like you said, it is a play on values that are socially acceptable to express to get what people want anyways.
As a result a recreational hobby gets dressed up as self care or pro-social action. There can be an element of truth to this of course, but I do think it introduces a lot of exaggeration and conflation.
Putting my biases on the table, the whole thing strikes me as childish and dishonest. Kind of of like a kid rationalizing to a parent how they will use some new toy to get their homework done faster.
You hit the nail on the head, IMO.
> Individuals feel the need to frame or justify and defend their individual actions and desires.
This, exactly this. I only recently realized this has been a huge factor for almost my entire life. There was always something more important to do than what I wanted. Parents wanted me to do things. School wanted me to do things. Religion wanted me to do things (courtesy of growing up in a proselytising Christianity-adjacent cult, 1/10 would not recommend). Later, in adulthood, it's family expectations again, then relationships, and then of course, work. The sum total of things I'm supposed to be doing, and that reflect good on me when I'm seen busy doing them, is effectively unbounded, leaving no place for any "selfish desire" such as... IDK, relaxing, taking a walk, clearing my head, watching stupid shit on the Internet.
Of course, those desires don't go away just because there's always something more important to do. But I can't just satisfy them without feeling like having to justify to myself and others, why I'm doing the "me thing" instead of the "important thing". Might be why I've struggled with procrastination all my adulthood - "I'm working" gets others off my back, and then it's only me I have to justify my choices to.
(As a kid, I didn't do "new toy to get my homework done faster", but I sure did the other thing - a computer to help me learn. It was a great argument, because it was partially true and my parents also heard it from adult sources (e.g. news programs).)
I'm not really sure why I do it, and why many others seem to. Some kind of insecurity? Like, I want to escape the neverending demands of other people without hurting my relationships with them, so I justify it in a way that makes fulfilling my own needs sound like either a) a critical, unavoidable maintenance work, something that's not really a choice, or b) it's actually doing them a favor, or c) it's capital-I Important. It's preemptively denying others the ability to counter "hey, what about me and my needs". A form of conflict avoidance, I guess.
I envy people who can just take vacations, or do hobbies, or whatever, without guilt or the need to justify it to others.
What's insightful about parent's comment is that it not only question the need for the new toy but also the need to do the homework faster.