You are correct that it isn’t really an essential feature, but it gives a nice boost in fluidity that I really enjoy, and directly ties into latency, which you mentioned as being important, which I agree with. Color accuracy still seems to be very good on modern flagships regardless of HZ, according to those who test those things.
The battery impact isn’t as bad as you probably expect actually, most newer high hz phone displays are LTPO, which allows them to scale down to I believe as low as 10hz, such as when you are reading or the AOD is on. I believe it will also scale down to match the frame rate of a full screen video too, which can also help.
As far as cost, I’m sure it’s not “free”, but now that OEMs like Apple, Samsung, and Google are all ordering them in bulk, I imagine it’s kind of just built into the category of display spec that they are ordering. For what it’s worth, the $300 Galaxy A23 features a 120hz display. Of course, Samsung makes the display, but that cost still has to be accounted for somewhere, especially as their profits are currently down 95%.
But yeah, overall I just enjoy a high refresh rate. My monitor, TV, iPad, and phone all support it, so I enjoy the consistency. I recommend trying a high HZ phone in person sometime if you haven’t. I find that it adds a lot to the fluidity of the UI both visually, and in terms of feel, as it feels like it follows my finger more closely when scrolling, for example. Of course, you can always turn it off and cap it at 60hz as well.