Many Skype users prefer to stay logged out of the service on their phones and tablets while not video chatting because of a fear of drained battery. If you remember, Google admitted that the Nexus 5 battery is currently experiencing faster battery drain due to the camera communicating with apps such as Skype.
Skype just updated the Android app to version 4.7, which will hopefully alleviate the situation. Just one other change includes message notifications in group chats being turned off by default.
Battery life is precious these days, so anything Skype can do to improve the situation is good news.