With the recent changes to energy prices to enter increasingly later game story dungeons (and special dungeons, actually) the sessions where you can actually play are getting shorter and shorter. And while the energy regen isnt the issue in my opinion, people could actually benefit from an increasing max energy cap you expand by finishing the non daily/weekly missions.
That way, the number of runs you can do with max energy remains the same if you actually keep playing at the dungeon levels appropriate for your team.