Actually certain methods in Pokémon Amie can increase Friendship.
"Although Pokémon-Amie can increase the friendship, it and affection are separate values and having five hearts is not considered maximized friendship, as levelling up with five hearts does not necessarily evolve Pokémon that require high friendship."
Things that increase and decrease the friendship value of a Pokémon in Generation VI:
Walking 128 steps
Massage in Cyllage City
Soothing Bag from Super Training
Using EV-lowering Berries*
Trading- Resets to base friendship
*These include Pomeg Berry, Kelpsy Berry, Qualot Berry, Hondew Berry, Grepa Berry, and Tamato Berry
Hope I helped :)