In iOS Safari, open tabs often must be reloaded when you switch back to them, either because you were looking at another tab, or because you had switched to another app. This is mainly due to the rising memory requirements of iOS and apps, and iOS devices having only one gigabyte of memory for a long time. iOS will delete tab data to reclaim the memory for another purpose, and will simply reload the tabs later if you ever switch back to them; but if you don’t have a network connection when that happens, then the tabs can’t be reloaded. Except if you save the page to Reading List. If you do that, then the sky’s the limit! Put as many pages as you want in there, no problem! It’ll recall as many pages as you want, on as many tabs as you want, for as many times as you want. I can’t for the life of me think of why the Apple engineers didn’t automatically put tab pages into Reading List, or even better do something equivalent under the hood, to be able to reload tabs without a connection. What’s really galling is that for iPhone (and sometimes iPad), reloading tab pages uses data from the cellular data connection, which for most of us is limited and expensive. Apple has consistently chosen to trade good battery life for slim hardware, and it’s limited battery life that prevents them from putting more than one gigabyte of memory into iOS devices. Basically, Apple is choosing to make us pay more in our data use rather than make hardware with sensible battery capacity.