I had to take one of my baby to hospital when he was 3 days old and I couldn't care less if I was being judged or not, or called "selfish".
His dad has as much right to be around as I had, we are equal parents, and I needed support after surgery. None of it is anyone's business.
Paediatric is usually faster anyway, but if people want support in A&E, have one adult running around making the wait a little bit less painful, a little bit more comfortable while the other adult is staying with the patient, good for them.
Busy bodies having an opinion on other families should mind their own business frankly.
I have been in A&E for my kids more often than I'd like , or other hospital appointments, and it's VERY rare I only see one parent, more often than not it's 2. No one is judging, they can't be, they're there as a couple (partners, friends, whatever)!