Though Mary-Kate has made some film and TV appearances since New York Minute - including an eight-episode stint in Weeds - she also thinks it "felt right" to step away from acting.
She said: "It just felt right to move away."
The pair run a fashion empire and though their Dualstar Entertainment Group has more than 30 full time staff, Mary-Kate and Ashley insist on being very hands-on with all of their business ventures.
Ashley told the new issue of Britain's Elle magazine: "We don't trust a lot of people. We are perfectionists. We've always wanted to be closely involved with everything, totally hands on - that's why it works. If we step away, it stops working."
Mary-Kate added: "I know it sounds controlling, but that's how it has to be. It is a big responsibility - but we've been doing it for years."
- BANG! Showbiz