That's what you get,Tom, for counting them before they're hatched.
Regarding the why? Beats me. Why not? Look at Mullica's routine, or Steinmeyer's, and others. Nobody bothers trying to rationalize the prop. The reason for doing the effect is apparent once the audience starts having fun.
Okay, Alan Wakeling's take on it was characteristically sophisticated and effective: "People ask me how magic is done, well I can explain it all to you now. First of all, the magician doesn't do the magic, you have to have something. For me, it's this little black bag. It's dark so that you can't see it against my suit, and it's small enough to hide in my hand..." I won't tip the rest, but there are plenty of reasons to reccomend the Wakeling book to anyone, and the egg bag routine isn't even one of them! Get it, and do thou likewise.
As for endings, I found the perfect ending for an egg bag routine a couple of years ago, and have never seen it anywhere. Don't know why I didn't think of it earlier. Just for you, Chrisdavid--consider this: go to a camping supply store, or a well-stocked gourmet thing-a-ma-jig store, and find a Minature Frying Pan. Mine is black cast iron, a perfect replica of the classic balck iron pan used in cartoons to whack people over the head. Only mine is about 8" across. It still weighs a ton, and only the most demented camper would seriously consider this a good idea (consequently, you can find these on sale pretty cheap)
Obviously, you script the routine to end with a final load of the pan. (The color allows you to be pretty darn sloppy about this. Note, load behind the bag, not in it) The egg makes its final appearance, then the pan, which is thumped onto the table with all proper melodrama.
I did this on a local television spot. People came up to me for a week saying, "you're the guy who pulled the bowling ball from the little bag!"
Here's something else that lends interest to the routine, and I did it, not quite knowing why, except that it was interesting: I use a white, plastic egg. I painted it with black markings, like the Gateway cow (or a Dalmation)the prop just looks funny, and makes you wish you had all sorts of lines for it, which, unfortunately, I don't.
Oh, and while you're doing your research, don't forget "Egg bag, Bag egg" from Routines Manipulation 1 or 2, Lewis Ganson's silent manipulative version of the trick, believe it or not. Very Zen, I recall in one phase you produce the egg from the bag, then vanish the egg, then vanish the bag by stuffing it into the egg and palming, and somehow ending with reproducing the bag, but it's got a white egg-shaped patch on it, which you peel off, and bounce on the bag until it inflates into an egg.
Or--and to me this is the "holy grail" of egg bag routines--try to end by going into Devant's "Eggs and Hat" routine. You know, the production of over a dozen fresh eggs, all of which are handed to a little boy to hold, which he can't. Many yuks as they hit the floor.
Child abuse for the whole family to enjoy!