because cloning ain't possible right now
"(and why, if someone installed hardware to clone a mag stripe, wouldn't they clone the chip too since it is in fact cloneable?)"
'cos it's not possible at present.
It's possible to intercept comms between the card and the terminal, maybe find out the PIN by a bit of decoding, and create mag-stripe data from the info you've gathered. This does not allow you to create a cloned chip card.
In fact, IIRC, the only current cloning method involves using an electron microscope to try to read the key off the in-chip storage.
"banks in the UK at least have this fantasy that it is not, and hold the cardholder responsible for fraud"
That's actually illegal if we're talking about credit cards, they are obliged to refund the money immediately you tell them a transaction is fraudulent.
I would be genuinely interested to read about cloning techniques if you know some concrete details though, I used to work on EMV systems (retailer, issuer and acquiring bank systems).
The most I can find is that some cambridge researchers have figure out it's possible to clone an SDA card (the cheap type which we ought to move away from) and then use it only for offline (very low value) transactions. Not much of a threat there compared to mag strip eh?