Two babies close in age

Why do some people hate on moms that have two kids close together. I saw a mom posting that she wanted another at 6 months postpartum and a lot of moms told her not to do it. Im just very curious why people think that a women that wants her babies that close in age are wrong and should wait longer? I know a mom that had her babies 14 months apart and love them being only a year and some months apart.