Countries like El Salvador and not so recently The Central African Republic are Trail Blazers in the aforementioned.
Bitcoin is no more a legal tender in Central African Republic and it happened not long after it was adopted as a legal tender 3 years ago or so. Also El Salvador had rescinded bitcoin as a legal tender as instructed by IMF, although El Salvador is still very friendly to bitcoin and it is still used like a legal tender.
What is stopping it's gradual integration?
Because bitcoin does not need to bocome a legal tender before you can use it as one.
I think that if Bitcoin continues to gain popularity among other countries, it will affect its price and the ability for so-called retail investors to acquire it. I believe that everyone on this forum has already believed in Bitcoin, and if it becomes more and more popular, it will work in our favor.