It always baffles me in Solo Queue when bot lane doesn't ward. Sometimes you get troll supports who won't ward (and for some reason they're always Nidalee) because some kid is butthurt that he was last pick and didn't get to go mid or top. And they either can't support, or won't, and don't buy wards.
And then the ADC dies to gank after gank after gank. Sure, you shouldn't have to buy wards - but you do. Yes, you need to be farming to get damage items to kick arse, and yes, buying wards would seem to be counterintuitive to that, but consider: if you die to jungle ganks because your brush isn't warded and the jungler knows it, how much more gold are you losing than the price of two wards?