Because our smart phones to run different types of applications that we use frequently throughout the day, you must be smart in the way it deals with multiple tasks. There must be a balance between the retention of these apps in memory so that users can return to them quickly when they need it, with a guarantee not to drain battery in the background, or at least not much.
However, it seems that the latter is something you do with Apple, at least with the iOS system 13.2, which seems that, according to the various users, it seems that the iOS update later this says aggressively to kill so to speak existing applications in the background in an attempt to improve battery life. Users they whenever they switch between apps for a minute and back again, is to restart it from the beginning.
For example, complained one of the users of that when he quit YouTube to reply to a message returned to the application, was to re-download the app already and lost the video that he was watching a moment ago. It seems that this is also a problem that affects the browser Safari where it seems that the windows remain open in the background, forcing it to reload itself whenever I came back to it.
It is unclear when Apple is planning a fix this problem, they are annoying too because they impose on the users waiting to download applications or undermine the progress that has already been made by the user.