How omnichannel banking can help a bank to perform better?

Looking for experts in the retail banking. Numerous influencers presented omnichannel banking as an efficient way to upgrade customer experience. Indeed, multiple industry reports show a variety of advantages given by channels interpenetration. Still, many banks seem doing nothing to meet the omnichannel expectations of their customers. What are the barriers preventing them from going omnichannel? What is the capable way to do it?