Why energy its bs

I have had this game for a while on my phone,but only started playing it today. I love how u have to use unlock all the attachments and camos etc. but the thing that makes me so mad and almost makes me want to stop playing this game, is that you have to have energy to play it and you can only play about 3 missions before you have to get off and wait 15 minutes for you to be able to play only one more mission!

Vectors awesome about Modern Combat 5