Shade is the most common reason a lawn dies. Bermuda grass needs 8-12 hours of sun per day. As trees mature they can create shade to your lawn and kill your grass. Other grasses like St Augustine and Zoysia can be planted in semi shade areas that may get 4-7 hours of filtered sun. In North Texas grass does well in full shade. Other common reasons your grass might die: lack of water causing heat stress, to much water causing disease, high traffic & long term neglect.