You mean the woman (she certainly wasn’t a lady) on the phone right? The one who thought that she could just order people around? And who did manage to do just that because the service guy was spineless?
The service factor. Grocery has a butcher, restaurant a server, bar a bartender. In this case, the butcher, or service person, seemed to make the decision. A poor one, IMO.
I wonder that myself; it’s always the same story - “Bad weather hits, everyone panics and buys up grocery stores!” We don’t do that here, but maybe that’s because bad weather is business as usual; we’d never go anywhere for six months if we didn’t go out in bad weather. 
I would like to change my answer; I think Shakes was actually in the right, and the bossy woman and the clerk were both in the wrong. If he walked away from splitting it because it wasn’t enough for his recipe, then that’s not a snit; that’s just changing your plans. He shouldn’t have had to change his plans, though - I think “first come first served” was indeed in effect here.
Essentially what this woman did was cut in line and pre-empted another customer’s order because she wanted it and felt that her want was more important than someone else’s want, and it worked for her, so she’ll probably do it again. And be put out if anyone ever calls her on it.
Well, she’ll get old and ugly (on the outside - she seems pretty ugly on the inside already) some day, and then won’t she be surprised.
If my original plan was for chili that requires 3+ pounds of ground beef to feed a crowd as you hypothesized, yes. If I were making it just for my own dinner, I wouldn’t need 3+ pounds. And if I were living somewhere where a cold snap meant people were buying up all the ground beef and nothing but the ground beef, I’d be too busy moving somewhere people aren’t nuts to do any cooking.
Next time, as soon as you enter the store, start a rumor that the toilet paper is almost sold out. Then head over to the meat counter.
Can I just say that the phrase is “first come, first served”. 
And the woman was out of line to demand the beef and the OP was not being unreasonable to want the 3 lbs.
This happened with my mom… she was a very pretty young woman, very petite, and she did that “cute princess” crap well into her 40’s… she had serious entitlement issues, and would have tantrums or cry in order to get her way. Then she got older, and I thought “Oh good, that crap won’t work on people anymore” but she just switched to “sweet helpless little old lady” mode. Goddammnit.
And then, another hot woman comes up and hollers “Don’t buy that!” resulting in another contretemps. And another. Now you have the makings of an old-time vaudeville blackout sketch, wherein you strike each other with rolled-up newspapers until the store closes.
I always wondered what happened to Zeno Marx…
Well, shit; you’re blowing my theory!
Someone upthread mentioned ‘dick’, so that would still work.
You know, I see this over and over again with a certain type of person suggesting that compromise is the way to resolve these situations.
So the pushy person ALWAYS gets a reward for being a jerk.
Screw that and screw the people that think that behavior should be consistently rewarded.
Everyone should’ve just stayed home and had Spagettios.
Hell, it’s not even a compromise, sometimes. Pushy people will push for some sort of deal or break on the price, and stupid managers will decide to just go ahead and let the pushy people have that price break rather than insist that the price is the price. Retail managers have rewarded pushy behavior, so that reasonable customers get screwed.
Most markets with the kind of meat counter where you have to ask the butcher to wrap the meat up for you (as in this situation) have their own grinder. Shops where the meat comes in packaged don’t usually offer to divide those packages up for you.
I think Shakes should have gotten the whole amount of ground beef since he was there first.
Worse than that, some stores won’t even do the right thing if you don’t throw a fit. Case in point:
Store in town we used to live in had signs over the registers touting their scanner accuracy guarantee: if it scans wrong, you get $X (I think it was three bucks) off the correct price. If price is $X or less you get it free.
What actually happened:
Item scans wrong. Customer points it out to checker. Checker changes to correct price. Customer points out discount policy. Checker acts like customer is making it up. Customer points to sign. Checker says “Sorry, that’s all I can do” and goes on. Customer asks for manager, checker says “Sorry, can’t call a manager for that” and goes on.
The only way to get them to honor their posted policy was to get loud.