You have to remember that those are policies put in place by the contracting company, not Facebook or the engineers that make the tools that these people use.
Facebook takes a hands on approach to vendor management: many of these policies are agreed with vendors at contract negotiation stage, but even beyond that, many are set and enforced day-to-day by Facebook employees working as vendor managers.
The other thing to note (and this is true of most outsourcing arrangements) is that, while engineers may respect these people and wish to provide good tooling, they're kept at arms length by management in terms of communication channels. Outsourced workers don't have access to internal ticketing tools, aren't party to any internal meetings on tooling (even those at management level in the contracted company). Engineers can mean well but that means little if they don't have any means to understand the needs of these indirect employees.
See, for example, Apple's supplier code of conduct: https://www.apple.com/supplier-responsibility/
Consider for yourself: if you hired a contractor to remodel your house, and you found out that the contractor wasn't giving their employees bathroom breaks, would you simply shrug your shoulders?
Facebook makes literally billions of dollars, they could easily pay more and provide better support to these people. They simply do not wish to do so.
The use of "contractors" in general is a shell game of abject responsibility.
If not, I'm sorry for the mixup - I'm just guessing based on your username.