Maybe your MOM is trying to get people into the habit of having productive short rehearsals. In fact, I agree with her . . . a group of grown people should definitley be able to have a good rehearsal in 45 minutes.
Sometimes we have bad habits, and the only way to correct those bad habits is to hold a line and say "Come up to the line, or stop playing."
When people are tired of not knowing the song, looking silly in public, and feeling lost . . . then they will come with their mini-tape recorders, practice at home, write down lyrics and get serious because that 45 minutes is all they are going to get!
Be Blessed