Bitcoin is still illegal in some countries for many reasons, I think thats because some of these countries are having trouble to control the bitcoin. because its uncontrolled and there is a possibility for a new way for crime activities, those are some other reasons that I often hear in the media.
But i do not think that most of the countries consider bitcoin as illegal. i think that most of the countries do not have taken any decision about bitcoin. They do not consider it as legal currency, but still they even do not have any official announcement about bitcoin as illegal currency. i think that with the passage of time they will turn bitcoin as legal currency just like japan. who already turn bitcoin as legal currency.