Yes, I know, but the light is generally above me shining down, so I'll take my chances that even if the sun is to one side and it's only 25%-50% effective: it's still better than nothing and I can deal with that in post better than no filter at all. Can't exactly do anything about it unless someone invents an auto-sun-tracking and self-adjusting filter, or a motorised one you can adjust from the ground.
So when someone says "Hey do you know polarising filters aren't perfect all the time" I ask: "And what have you got that's better? Nothing? OK, I'll just carry on with this then. Cheers!"