I've never shipped chicks or had them shipped to me, but I do send and receive reptiles. If shipping chicks wasn't a thing the local farm stores would never have anything that I would want. Locally it's mostly bym, barred rock, Rhode Island red, black austrolorps etc. Most common breeds and mixes of those. I did a lot of research before getting my chickens and although we ended up with a mixed flock (when the chicken math set in) our main flock consists of Crested cream legbars. Without shipping we would have never been able to aquire this breed.
I have my own issues with hoover hatchery, not because of shipping, but because of not breeding to the sop for most of their breeds. Cream Legbars are an auto sexing breed, males and females should look very different at hatch. Out of 15 chicks we got, only one was supposed to be a roo, we had 5 roos and 2 of the hens are actually a mix making them Easter eggers. If you breed low quality, you lose the auto sexing.
As for the shipping. As a reptile breeder, most of the good ones will not ship in temperatures below 70° for tropical species and not below 50° for temperate (northern) species. Heat packs can help, but they can also hurt. Most generally get to about a max temp of 115° about 30 minutes to an hour after being activated. They also use oxygen, so a completely sealed box would mean death. There's also phase packs witch help to regulate the temperatures. Ideally shipping would only happen at temperatures over 70° with no additional heat, or over 60° with a heat pack and phase pack. The phase pack will reduce temperature spikes while letting the heat come through slowly and more evenly. They have to both be secured to the top, side of the box with enough head room as to not be in direct contact with the animals.
It's really complicated, and I hate shipping animals, but there's not always local people who want designer reptiles or poultry.
I'm sorry for your loss and the terrible customer service. I definitely believe that the company selling the animals should take proper precautions when shipping.