Republic of Ireland international O'Kane brought down the curtain on four glittering years at Vitality Stadium when he joined Leeds United for an undisclosed fee on deadline day.
Howe told the Daily Echo: "Really, the decision has been made for the benefit of Eunan's career. If we can't give him that window to play, we need to make sure his career doesn't stagnate.
"I'm sorry to see any player go. Eunan has been a massive part of our recent success. He has always shown a great attitude and been a great team player.
"He's never moaned or been a disruptive influence when he has been out of the team.
"He has been invaluable to our climb up the leagues. He more than played his part going back to the Championship and League One days. He really did rise with the challenge of the level.
"We wish him well and hope he has continued success in his career. He leaves on very good terms, as all our players who have been here a long time have."