I don’t think it’s as nefarious as that. It’s probably just that jury duty is rare enough and it would be controversial enough for them not to pay that they don’t bother dealing with it.

There's also a strong appeal to civic duty, both for those chosen for jury duty and for employers to pay them. And generally, at least where I am, people who try to weasel out of jury duty as well as companies who don't pay employees during jury duty are viewed in a bit of a dimmer light.