I wasn't clear enough and I apologize. You can use cookies but they will only be within the context of a singular app's browser. For example, suppose that you use two web browsers on your Desktop, Chrome and Firefox. If you visit xyz.com on FF, some cookie information will most likely be stored. However, if at a later time, you visit the domain on Chrome, it will not have access to the same cookie store.
This becomes important in the context of third party cookies that want to track you across apps. Hence why cookies are not a reliable method of identification on mobile.
This becomes important in the context of third party cookies that want to track you across apps. Hence why cookies are not a reliable method of identification on mobile.
Hope this clears it up. :)