In a lot of northern states in the winter, one of the previous societal expectation was that you'd turn your lights on whenever it was snowing - which, around here, is pretty much constant, as is the resulting salt residue on windshields. It's not very bright either because the sun at solar noon peaks at about 20 degrees above the horizon and is behind perpetual clouds.
But that's still bright enough that a lot of automatic headlights don't turn on.
Mine don't, and my car is pretty new.
The problem is: I leave my wipers on almost all the time, rain or shine. With automatic wipers, there's little reason to turn them off, so I end up just leaving them on most of the time, and then when I get splashed by a passing vehicle going through a puddle or something, the wipers will automatically clear the windshield.
You wouldn't want the headlights to turn on all the time when wipers are on automatic mode. Now why they don't turn on for regular modes, I'm not sure, but probably consistency: if you don't turn them on for automatic mode, but you do for regular mode, then that's going to be too confusing for the driver. Maybe they should come on when the wipers are activated in any mode and stay on for a certain number of seconds (by "stay on", I mean actively clearing the windshield, not just waiting for water to appear). But this might be too unreliable in practice?
But that's still bright enough that a lot of automatic headlights don't turn on.