One of the major stress points for many relationships is how the chores get divided. Who ends up doing what to help the home stay clean and tidy can be a source of real problems. It's not hard for one partner to feel taken for granted if they find themselves constantly cleaning and cooking while the other one doesn't.
Now, how the labor gets divided is entirely up to the couple involved, but as one study shows, how things appear to those outside the relationship can have a huge effect.