A vort from the heilige Rabbeinu Isser Mendel Shmaya Osher Tennenbaum (RIMSHO”T):
Q: Why do we go collecting on Purim night when it isn’t part of the mitzvos hayom?
A: Because many people have trouble reaching the madreiga of ad d’lo yada, and some even think that there is no mitzva to get drunk rachmana litzlan. So the yeshivos provide a service by sending bochurim around to harass the baalebatim at late hours and drive them to drink! 😉