I hope i do not get flamed by bigots for this but this are just my honest opinions
1)They are not forced into the language therefore they get to find out more before learning it
2)They can learn it at their own pace
3)MOST of the them they learn conversational Chinese only, my conversational chinese is so-so but my written chinese is horrible.
The Chinese Language is one of the most difficult languages.
The only easy part is there is no grammar.
Eg. Yesterday I eat. Today I eat. Tomorrow I eat.
He sing. I sing. She sing.
Somehow I think grammars are quite redundant.