At our chapter, alums are these mystical beings who we rarely see but who always send us truckloads of homemade cookies & candy during finals week.
Alums don't come around in person very often, from what I've seen, so maybe that's the reason we sometimes forget about things like standing up when they enter the room. I'm not sure...I think it's more the case, though, that we were just never taught those finer points like that; I remember hearing it once as a new member, but I haven't had to remember it too often.
As a rule, though, I think our alums are great! They do a lot for us, whether or not we realize it (I just noticed this last year when House Corp. came to talk to us). Maybe I can put a reminder on the announcements at next week's meeting that we should make sure to give alums the respect they deserve!