Why are the little girls at the beginning wearing dresses the 60s?

I know this was made made back in the mid-80s but it's pretty weird to see them wearing those kind of dresses. I'm referring to the part where they make fun of that dog wearing a cone. They're wearing dresses from the 60s and this was made and set in 1986 not 1966.

They also had this same problem in the Nightmare on Elm Street remake where we see Nancy from the Preschool flashback wearing a blue "Alice in Wonderland" styled smocked dress and those scenes were supposed to take place in the late 90s or early 2000s, not the late 50s or early 60s, which is when little girls wore those. No wonder Freddy Krueger molested her and her friends because in one scene, he said he always liked that dress.