This is a weird solution for a web browser proud of their concern on security and their supposedly strong users protection.
The problem started with bad designed sites sending too many cookies requests. Firefox had three options: Accept all, Deny all, Ask me every time. To solve the mentioned issue, Mozilla team decided to trim an option, “Ask me every time”.
People filed a bug you can find here: https://bugzilla.mozilla.org/show_bug.cgi?id=660507 and here: https://bugzilla.mozilla.org/show_bug.cgi?id=606655
As far as I can see, it’s a website’s issue not a web browser so I can’t understand why the heck they removed that option. Personally I didn’t use it and some may say there’s many addons to manage cookies, but isn’t the point. If it isn’t a Firefox problem and it isn’t a burden to maintain, why taking it away?
Moreover, accepting all cookies implies to accept third party cookies as well. Something not everyone likes to do. Again, there’s others options, there’s even other browsers, but that’s not the point. No science progressed saying “If you don’t like it, go away”. If something doesn’t work you investigate and create solutions until it does. And if it’s not your fault (as in this case, is a website bad design) then you can warn users or even make a workaround, but not trimming options for the sake of… Of what?
If you want and can, add your comments on the links above. Otherwise, your options right now are following sheepishly Mozilla decisions or changing your browser.