You forgot the main reason:
FANBOY WARS! 
It's possible that someone else has said that already ITT, but I didn't read all the posts before I made one of my own 
That's the main reason, although I doubt anyone would admit it. Well, I suppose it's partly covered by the "supporting arguments" option.
Also, I enjoy facepalming and raging when butthurt over sales that don't go the way people want leads them to say stupid things and get themselves trolled by people who weren't even trying to troll them.
Actually, I wouldn't be surprised if trolls didn't take an interest in sales in order to help them find targets. Trolling isn't my thing (no, really), but if it was, I would keep an eye on sales to see which console was doing badly and focus my trolling on its fans, since they'd be most likely to fall for it 
