Own terms. In all states, companies are forbidden to fire you or retaliate against you for serving on a jury, but they generally aren't required to pay you.
> When an exempt employee reports for a full workweek of jury duty and does no work for his or her organization, the employer is not required to pay the exempt worker for the week. However, _if the employee does any work for the organization, including checking and responding to work messages/emails, the employee is considered to have worked during the workweek and is entitled to a full week of pay._
So basically if you check your email then you are entitled to the full week anyhow. One mess up and an ensuing lawsuit would blow the whole average year's worth of jury duty savings from _not_ paying your juror-ing employees.
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.