On this site (which logs you occasionally), it can be frustrating to have everything deleted after spending a long time typing something out. However, many other websites, such as banking websites or school websites, should remove all typed information when logging in. Many of these websites have information that can be fairly dangerous to a persons identity security if discovered. It would be nice if some websites gave you the option, but I am not a web developer and do not know the feasibility of such an option.
I know that it is highly unlikely but it could happen, people can then guess the password or username and hack into private accounts, like bank accounts and you could lose a lot of money, or a lot of privacy, especially if it is the same password for all of your accounts
Debate.Org will often log you out over time without telling you and then you find out after you just typed something and then after logging in it takes you directly to the home page and everything is lost. Backing up doesn't help either. Once this happens anything you just typed is doomed. It would be much better if logging in would send you to the page you were just on with everything there still typed.