In the UK, it's not unusual for employers to offer private health insurance (or at least, it's pretty common for profesional jobs - I can't comment for other types of jobs!). From their point of view, it's comparatively inexpensive and the cost is probably easy recouped from their employees being able to get health problems dealt with faster than they might on the NHS so they're off work for less time.

Edit - Given that we've got the NHS as well, losing your private coverage isn't such a big deal. It's nice to have, not a must have.