Why have I lost my accent but my parents have not?

I definitely think that some people are accent sponges and other people aren't. You pick up dialects and accents from the people around you when you're learning to speak. This gives you a similar accent to your mum or dad. Accents are, afterall, just imitation. The reason things like this occur, is that if you get a group of people together in one place, the strongest people tend to attract imitation amongst the other people. So if someone has a particular way of speaking, people try and blend in and talk in the same way. So someone with an English accent in America is likely to pick up some of the American accent.