Just as a data point... I like and heavily use the core libs... And not once i used arrow, request or simplejson, while knowing them, because i didn't feel the needs
Arrow seems particularly useless as it just wraps stdlib datetime and its awful 10 byte size rather than moving to an 8 byte representation like np.datetime64 uses.
Just because you haven't found a use for it doesn't mean it's useless.
The stdlib datetime class is terrible and desperately needs to be wrapped. Arrow is a good wrapper. I don't know what you're on about with counting bytes.
I've wrapped datetime for company work (pre pandas, pre datetime64) to make sure it follows the rules of the data analysis platform we developed (adding functions for moving to next month of year based on various financial calendar rules for example). I wish I hadn't done it and had just wrapped a boost_datetime since the performance of datetime is slow when you have a large timeseries of them. The performance is especially unacceptable if you also have timezones attached to your datetimes.
Now we have pandas, yay. But I don't see why one would use arrow. If you're patient enough, could you explain why you would use it? The website doesn't seem to be very convincing.