They get paid to offer you assistance; but, there are several factors mitigating this. One, they run on skeleton crews in order to give you the low prices. Want prices and help - pay more. They also pay their employees the lowest price possible and work them like dogs. The average resteraunt worker makes more than a Walmart employee does in this town. Want fries with that?
Next is the consumer mindset. Most consumers go in to merely shop. Some go in to kill time. And others show up just to show their superiority to the local servants. Yes, believe it or not, many in this world (liberals largely) think themselves superior and think the local burger flippers and shelf stuffers exist to wipe their butts for them. Walmart's workers are people, not your personal butt shiner. If you go in there to be lied to about how perfect you are, you might get the truth instead. If you go in there to mess with them, don't be surprised if you get it fed right back to you. And don't be surprised when after an 8-16 hour day putting up with that stuff that they will smile merely because you showed up to give them grief because their employer will neither pay them a decent wage nor give them the help they need. It's easy to shoot fish in a barrel. They didn't make the barrel. They're largely there because they have bills to pay.. not for your amusement or harrassment. And no, I don't work there. But I did 10 years of retail and know exactly the kind of jerks that have to be put up with.