We both have wills and we have chosen my sister and BIL for our DD if anything horrible were to befall us. She has her big sibs (now 17 and 21) but we chose my sister and BIL because they are adults, established, and would make good choices. They also have a similar life-philosophy, parenting ideas, and religious preferences. If at the time of our demise a guardian for DD is needed and her brother steps up, then I'm OK with that, but we didn't want to saddle a younger person. We didn't pick my mom or his parents because we felt that a younger couple would better handle the challenges of a child.
It is, IMO, silly NOT to think about it. DH and I both have term life insurance that would pay off the house and give the surviving spouse some money to take care of the family in the event one of us dies.
DH's friend was only 49 when he died of cancer. I have a friend now in his 30s with a kid on the way and a 6 yr old and he was just diagnosed with leukemia. We all hope he survives and sees his grandkids, but life throws all sorts of things at you and you need to at least think about it.
If no one is "perfect" (my BIL is a little serious and I hope his own son gets him to lighten up a little), then pick the best choice and hope you never use it. My sister's godparents were actually our father's sister and BIL and after the divorce, well, that was no longer going to be the best idea. Mom changed her will so that my sister's guardian would have been her brother (our uncle). It was never needed, but you can change if you need to.
I'm using godparent and guardian interchangeably but they don't have to be.