This depends on what you mean by "a pure market solution", as most workplace safety laws were put in place to make things more predictable for employers, rather than helping employees. The 'old system' in most places involved one-off lawsuits with somewhat unpredictable outcomes.

And you know what? It's totally fine. I absolutely don't want my people in the building until it's deemed safe. I can't really imagine another stance.

Amazon is so big that it's employees really are just cogs in a machine. They really couldn't care less about these drivers.

Virutally no jobs on the planet are worth such a direct risk. Especially when you can just wait it out. It's highly likely there is absolutely no pressure to have those delivered soon besides "we want them soon."