I have been seeing this for many years, now. It's not just you, it's not just Walmart, etc. There is nothing like working retail to completely loose hope in mankind. I manage a nutritional supplement store that carries higher end products, so you have to have some cash if you're shopping there (in other words, these are the opposite end of the financial spectrum compared to Walmart shoppers). Yet, I too watch parents let their kids run around, mess up price tags, move around products to totally different aisles, try to open products, etc all day while their parents just stand there, totally consumed by their consumerist needs. It doesn't even phase them that this is going on. In fact, they're pretty much oblivious to it. Yet if anything were to happen to those kids (i.e. tripped and fell, and cut their heads open), WE'D be the ones getting sued for THEIR negligence!
Sure, some parents fear disciplining their kids due to legal issues, but I think the FAR bigger reasons for this is because parents want to be seen as "cool" and "friends" by their kids, and even more importantly, people are unbelievably lazy nowadays. It is no wonder video games have taken off like they have. They've become the new babysitter. Give them $60, let them go down to the local Game Stop, get their favorite new game, and shut them up for hours at a time. Hell, one of my sisters used to babysit, and at LEAST half the time, the moms were home while she was there! They just didn't want to deal with taking care of the kids.
I have also dealt with my share or moronic drivers who don't care about who they're wrongfully inconveniencing, or who they may be endangering with their driving antics (cutting you off to get in your lane, slamming on their brakes with no turn signal because they just realize they need a right here, etc). And don't get me started on people's lack of appreciation when you do something for them. I'd say at LEAST half the time, I don't get acknowledgment when I hold a door open, or allow them to get in front of me in my lane, etc. For being as uncommon as it has become, you'd think it would warrant some kind of reaction from most people. I still remember going to Chili's with my sis a few weeks ago, and there was a lady on a walker (whe wasn't that old, just had some kind of hip problem) struggling to open the door. There was a teenage guy and girl sitting on the outside bench RIGHT THERE, and they didn't do anything. So I sprinted to the door just as she was starting to fall, and grabbed her by one arm while grabbing the door with the other. She thanked me up and down for doing so, and offered to buy as drinks 3 times, which I declined, telling her it was unnecessary, but thank you. Meanwhile, the 2 douchebags continued to yap away, just sitting there.
This is what this country has come down to. Gone are the days of the original Americans who built this country, and set up its initial ideals and principals of taking pride in your work, and working your ass off till the job is done right/to get what you want. What we are left with now is a collection of self absorbed, oblivious, lazy, whiny, apathetic people that believe they're entitled to everything, and have no sense of responsibility. We don't care about ANYthing outside of making things as easy as possible on ourselves. Why are we so behind on everything in this country compared to other industrialized nations? Why, in spite of our wealth as a nation, are we not on par with Europe or Japan when it comes to schooling, electronics, cars, etc? Simple. Because we have no pride in anything we do anymore. Oh, sure, we CLAIM to be very proud people, but let's get real, talk is cheap. When it comes time to put your money where your mouth is, most people can't walk the walk. We clock in late for work, surf the net while the boss isn't looking, do a half ass job/the absolute bare minimum on the few things we get around to doing, pass the buck on the things we don't want to do to the next guy, and then we go home "tired after a hard day's work", and complain that we don't get paid enough, or that our benefits suck. We talk about how much we hate being fat, and want to loose weight. We claim we want it very badly, yet, we don't want to put any work or effort into making that happen. We scour the stores, the net, the magazine ads, etc looking for a magic pill that will allow us to loose the weight without having to go to a gym, or making any sacrifices in our diets. When it comes down to it, we are all talk. We have grown weak and pathetic. We want everything handed to us on a silver platter, because we are ENTITLED to it!
The problem with such a lazy and apathetic society is that it makes for the types of people you're describing. Rude, inconsiderate, lacking any class, manners or self discipline, etc, and I don't see it getting better any time soon. In fact, it will only get worse as we keep ACCEPTING the constant lowering of our standards instead of being appalled by it. How can one conceive ever reversing such a trend? All you can do is take care of your own, and figure out how to best handle what's thrown at you by the brain dead masses.
... but I just can't believe how selfish people are nowadays. I could go on and on and write a book about instances where people are just jerks in an unnecessary situation. 
