There are a few items that are so hard to mess up (e.g. toilet paper — it's just a long roll of paper!) that they are indeed perfectly fine at the dollar store. But all the food and a lot of the other items are really awful, and it makes people wary of relying on the stores for anything.

I don't know, maybe this is a regional thing and it's only been that way in places I've lived while other places have awesome dollar stores. But I've had friends who lived in places only marginally better than slums who still would only very reluctantly shop at dollar stores because they didn't trust that the candles wouldn't burn down their house and the food wouldn't poison them.