Meghan C. answered 09/21/20
Patient and Passionate English Tutor for K-12 and College Level
You're on the right track with wondering if there is a cultural background to this poem. I would suggest doing research on the author and the time this poem was made for more context.
As for the specific reason why there is a waistcoat instead of any other type of clothing paired with "leering" take the setting into consideration; where are they?. There is one more piece of clothing that is personified in this section. Where are they standing vs the waistcoat?
Also take into consideration what "leering" means. In what context does this word usually show up in other works or descriptions? After taking into consideration their setting, the word "leering" can reveal just how the author felt about this event and the people taking part in it.