it’s both. the exploitation elements are what the ads for the films were based on. those films didn’t have huge production values or big movie stars so they focused on those elements to sell the films. it started way back with the roadshows in the 20s. but the exploitation elements were not always lurid elements of violence and sex: when rock’n’roll exploded in the fifties American International Pictures (the most famous indy company of exploitation films) did a serie of films about rock’n’roll, high school and teenagers (rock all night and carnival rock being two of them)… the exploitation elements were then rock’n’roll, teenagers, fast cars, etc. Here’s a piece of the radio ad of the AIP’s double feature of Dragstrip Girl and Rock All Night:
“Some kids like to dance. And some kids like to kill! Speed crazy! Car crazy! Thrill crazy! Fun-loving teenagers, free-wheeling and fast travelling in Hollywood’s newest bag up, crack up, smash up double feature of fast cars and fast living”
those are elements you wouldn’t really consider exploitative anymore, but still.
Re: Halloween, just check out the trailer here - YouTube
You’ll see that it focuses on a lot of exploitation elements (a killer child, young girls, violence, a killer that’s is “pure evil” and inventive killings). there is not one credit for the actors, not even Donald Pleasance! that’s exploitation! 
