This is a currently limitation as outlined here: 

My best proposed solution is to add a table to the Audience Dashboard, along with an option to filter. That dashboard already aggregates data for Unique Users and Total Page Views. Those are the two insights I’d like to see at the start.

While using external tools like Google Analytics can give the insight, it is an barrier to adoption of custom pages and impediment to community management. User and View insights help: 

• Measure impact and ROI of that custom page
  • Is it getting the engagement we expected when it was built? 
  • Is it having an impact that we might replicate with similar custom pages?
• Indicate success of the custom page’s strategy
  • If it’s views are low, consider the navigation paths and Information architecture

In the beta for Control Home, I’ve highlighted that I’d like to see these insights on that upcoming feature. But having the analytics built is an prerequisite to that being possible.