Why does Gaara still have dark circles around his eyes? It is stated that Gaara has his dark circles around his eyes because Shukaku won't let him sleep because Gaara will lose control if he does. 

After the extraction of Shukaku, Gaara still has these circles around his eyes. Why? Is it only style or does he still suffer from insomnia?
I'm more inclined to agree with SingerOfTheFall's answer.
Upon Gaara's birth (Shipuuden episode 297 and Naruto chapter 547, page 4), he already had his dark rings around the eyes.  



I know he already had the Shukaku sealed inside him, but I find it a bit odd that he was born suffering from insomnia.
Plus, the translation I read of chapter 135 does not refer to the dark rings, but rather to the 'bags under his eyes' (although this could be a problem with the translation...):  

  

Furthermore, as SingerOfTheFall said, there are several other Suna shinobi that have dark rings around their eyes, including Gaara's father when he uses his Gold Dust:  

  



On a side note, I think it can also be the influence of the tanuki (the 'inspiration' for the Shukaku) in the character conception, since the tanuki too has dark rings around his eyes.  

  

So this trait could be somewhat similar to the whiskers Naruto has from the Kyuubi. He had these whiskers even prior to being the Kyuubi's host:  

  

This could mean that the dark circles are a character trait (conceived upon character design) that were a result of the Ichibi being sealed in Gaara even before his birth, thus being present even after the Bijuu's extraction.