Ultimately my comment was about entropy: a date with a timezone contains more information than a date alone. The technicalities about database columns, inaccuracies or privacy implications do not change this fact.

I argued that keeping this information instead of discarding it is often useful and gave a few examples. I understand that sometimes systems can get by with only storing local dates or UTC dates but sometimes a system needs to be able to deal with both and keeping these extra bits of information is the only way.