US Android users buying decisions

Let me ask you guys a question about android and your decision to buy phones, I'm speaking directly to US Android users.
I hear plenty of times about wanting stock android on your devices all day long, it's probably the number one complaint/wish I hear here on the forums about any new Android phone that comes to market, So if US Android users want a stock android why not buy a stock android phone? Why buy a phone with a skin and complain about it because it doesn't have stock android? I know many people might say that the hardware isn't always good on Nexus devices but now US customers have the GPE phones as options which are seen as the best high end phones plus stock android.
So why does the complaining about skins continue to arise when stock android options are available?