It's a rhetorical device: present an assumption favourable to the viewpoint you're arguing against and show that even with that assumption, the opposing view does not make sense.

I understand the rhetorical premise and retorted by identifying the logical flaw @Obversity presented thusly:

> There are plenty of dev companies capable of doing this and doing it well.

The position argued by both @Obversity and @tlb is that somehow "private companies" can satisfy what the IRS is required, by statute and Congressional oversight, to provide. "Private companies" are not subject to such constraints.

Hence my reductio ad absurdum conclusion of:

> Unless your premise is that one or more startups can replace federal tax collection.