Confused parent

So quick question. I send pictures to my child’s fathers parents every now and than of my child since they don’t live in the same country as us. On some of these pictures my daughter has her tongue out. So his mom first says “oh please put her tongue back in her mouth. Never let her stick her tongue out” and says it multiple times. Than his dad says to make sure to “always close her mouth to cover her tongue as she grows” I don’t need a big problem with this but it is getting on my nerves. I asked my child’s father and he said he doesn’t know why they are saying it. So is there any particular reason why they want me to put her tongue back in her mouth? She turns 8 months this month.