You don't have to get enough investment to compete with UPS - you just need enough investment to start a company that earns you more money than you'd earn than you could working at UPS. These are very different statements! But yes, even to make more than $20 an hour, it's "hard work" - which people just wanting a higher salary don't appreciate.
It's not a "hard work" issue, it's more that even in industries that don't have barriers to entry that look like a lubed up cliff face, the majority of startups
fail, regardless of how much hard work is put into them, and people friggin'
know that. For the sort of folks that are involved in most strikes you see in the US, they don't have the means to reasonably weather that sort of failure. Never mind it's a bad joke to suggest they're able to even give an attempt at some sort of small scale courier service. Scale, existing infrastructure, and previous contacts matter a hell of a lot for things like that, and between the major services and existing smaller operations the field is really bloody saturated.
Telling people to just go do a startup might as well be telling them to go cut off one of their legs to get disability, it's probably about the same chance of them ending up on the streets or worse.