Why Mandarin is more difficult to learn than Cantonese for 2nd generation oversea?

I have seen more children raised in Cantonese speaking families retain their language skills than Mandarin speaking ones. Why? Environment.

Language environment is critical in mastering a new language. Both Mandarin and Cantonese speaking parents talk to their children in their mother tongue, but I don't think that is enough, especially for teenagers. In this stage, teenagers seek for peer recognition. I remember when I was in junior and senior high. Besides schooling, my friends and I started to pay attention to entertainment industry, and we have board topics of games, TV soap episodes and songs, etc.. This is where differences lay between the two mentioned above language environments. In Cantonese community, people manage to provide children with radio programs, popular TV series, songs, celebrities and magazines. The impression left for children is COOL to know about all these. In Mandarin community, I don't think parents even care about entertainment industry to children. Children shame about speaking mother tongue, which is the failure of traditional education.