Now Ben Cooper could have been just another costume company, but the issue of licencing was the big difference. When Ben Cooper (and others) started getting licencing for various movie, cartoon and TV characters-Halloween masks as we know them changed.
Instead of being a "Fairy Princess" a girl could be Disney's Cinderella. Instead of a generic werewolf, boys could be Lon Chaney's Wolfman.
Yet even then, the characters and role models expanded-Girls could become Miss Kitty from Gunsmoke, or maybe a NASA astronaut. Boys could become their favorite cartoon character, or Han Solo from Star Wars-the choices became widespread. As the sixties went on, Girls started even having girl heroes or villain characters as the women's rights movement went forward.
The technologies allowed this growth: with pvc plastic easy to mold and churn out, the different varieties of masks and choices became widespread. That combined with the inclusion of "smock" costumes, and it really is little wonder that the era of witches and goblins was greatly reduced as time went on, though there still enough "traditionalists" who could find a generic witch or ghost mask-but the inclusion of licencing really changed Halloween from the "scare the spirits away" aspect to role playing favorite characters.
The PVC movement would carry forward into the late 70's, before the introduction of latex and rubber would create a whole new aspect of realism.....