Most 16:9 laptops have thick bezels. They could have 16:10 in the same space. 16:9 is just cheaper. Most 16:10 screens add rows to a common 16:9 resolution. So

Most 16:9 laptops have thick bezels. They could have 16:10 in the same space. 16:9 is just cheaper. Most 16:10 screens add rows to a common 16:9 resolution. So 10:16 is even better than 9:16.