As to "why anyone would buy these", I bought a bunch for my physics lab. All they usually measure is 0-6 volts. They're cheap enough we can use two or three per group. I think the last time I bought them I bought two dozen and spent under $100.
And when I want to measure something higher, like the secondary circuit of a Geiger counter (600-1000v), I can hook it up, turn it on, turn the circuit on, and not touch it...it measures the HV just fine. I haven't had one lose the magic smoke yet. I don't let the students do any HV work of course, not with these meters. But in a pinch, I find them useful for careful (but rough) measurements.
If we have the money, maybe I'll upgrade the lab set to the Aneng meters -- those are a bit nicer, but not so horribly expensive as to make the central office have a coronary.