Okay, well this is actually super cool, thanks for driving my attention there. It seems that the word for this particular behaviour is "Nyctinasty
I think the short answer to your question appears to be “we don’t know”, because nyctinasty has been observed for millennia but there isn’t a clear, conclusive answer. In some plants that are open at night, it may be that they are pollinated by bats or nocturnal insects, but one of the open questions here is “does nocturnal nyctinasty happen via the same mechanism as diurnal nyctinasty?”. By that, I mean “does a nocturnal plant (like moonflower) use the same ‘muscles’ as a plant that’s open during day, like water lily?”.
I don’t recall it mentioning water lilies, but a book that you’d probably enjoy if you’re curious about this stuff is What a Plant Knows by Daniel Chamovitz. I remember there is some really interesting stuff in there about plant circadian rhythms, and the information is presented in an accessible and entertaining manner
A somewhat cheesy quote that helped me a lot is “you can be the juiciest, ripest peach in the world, but some people just don’t like peaches”. I used to try way too hard to be likeable and I agonised over people who didn’t like me.
There was an instance of a colleague being rude and unprofessional to me, and under the framework of “they don’t like me and that’s why they’re being unkind”, it put the onus on me to change, which wasn’t reasonable. It should be possible for people to not like each other in a working relationship while still being respectful and productive.