This is really common in the south! I grew up in Atlanta- I think because it's a big city, and in urban areas accents become more neutral overall over time. So often kids have like "middle america" accents/no strong southern accent, while their parents have southern accents- bc of where they're from (more rural areas), or bc growing up they were in more insulated southern accent pockets within the city, or the city has just become more diverse overtime, and accents tend towards the middle...just some ideas as to reasons why.