The question should be self-explanatory.
Your first set of children as brand new parents is an adorable set of identical twins (or triplets etc.). The hospital generally has good systems in place to keep of individual babies but do most of the parents or other family members? It is easy to put them in different colored socks but what happens when you put them down for a nap in the same crib and didn’t anticipate that both of them were going to pull them off and mix them into a pile. What if you put them in a bath confident in your ability to tell them apart based on some system you came up with and you find out that that your supposed system is completely water soluble.
I know it isn’t the end of the world if little Emma and Elizabeth get switched when they are two weeks old but it seems like it could cause some distress to the parents or other relatives if they get themselves in a situation where they really aren’t sure. It could be a problem for the kids when they are old enough to have some sense of identity but can’t communicate well yet. I know that no children are truly identical some people are much more observant than others.