are nightclubs a good nite out wit the girls or just a meat market as my partner likes to call it??

my sister inlaw is 21 and shes married with 2 kids shes never been to the nightclub and she wants to go now but her husband keeps telling her its just a place to hook up and then he will spitefully say "well i'll go to the nightclub the following weekend!". she has asked him to go with her but he wont so im not sure why hes acting like that. Are night clubs just a place for a hook up or can you just go there for a night out with girls innocently?