Samsung, HTC, LG are selling Android. Their other phones aren't selling really. If Nokia sold Android, they would be far behind in the Android market, and won't sell too many Lumias either.

Nokia essentially dropped Symbian two years ago.

They sell low cost Asha phones here in India (and probably in SE Asia), which I thought was an S40 derivative. (It seems so.)

The latter being around 3% of total smartphone sales, comparable to the marketshare of Bada OS two years ago.

Breaking into smartphones is hard. Nokia knows than Windows Phone isn't going to be shuttered. Windows Phone 8 was the first real Windows Phone OS. I recently was at a Nokia showroom. The $140 off-contract Lumia 520 was smoother than my Nexus 4. You should try it.