ELI5: why can’t I put windshield wiper fluid directly on my windows?

I keep reading that this is a bad idea but I don’t see why. I’m wanting to put winter grade wiper fluid directly on my windows before a snow storm to make the ice easier to scrape off when the weather hits. My reservoir has a leak, so I can’t use the intended mechanism to use it. Besides, even if I did, it won’t spray it onto my side and back windows. My fluid has a freezing point of -25 degrees, which is more than enough wiggle room for my area’s climate