You mean like your mail and social media accounts? I think that sort of defies the entire part of the smartphone.
Anything you'd rather not be compromised, yes. The smart phone is useful enough as a data storage, transfer and communication device that can run arbitrary programs for utilitarian reasons or perhaps entertainment. As for social media, will the world end if you don't access Facebook on your phone? I realize that it might be difficult for some people to understand, but not everyone cares or cares equally about social media.