Some of them may be truly interested in getting to know you but most of them are simply following the custom. So when Japanese people have a chance to interact with foreigners outside their work, they may feel lost for not knowing how to appropriately interact with them. Outside the work, this uchi/soto relationship is vague and it becomes even more confusing with foreigners.
This is also why foreigners (soto) have a hard time being truly accepted into Japanese society and those who wish to become Japanese citizens (uchi) face many obstacles.