1.) Play without people knowing what to expect (ie. if I've played someone 30 times I know their playstyle and adapt to it, if they played me anonymously though they'd have an advantage)
Only reason any alts need to be anonymous. Other than this one:
7) Because it's funny to make an alt every now and then after myhand (and other random people) does, and watch how foolish people are in thinking myhand's (and others') alts are mine.
"Hahahaha our accounts are anonymous so people don't know who we are ahahahahahahaha" grow up.
5) So you can say stupid/funny/random things in the chat and try to have fun with it.
Stop taking yourself so seriously.