I think it depends on the type of person and on the type of job. As an independent contractor, you're more likely to have to at least be reachable while on vacation, due to the nature of the work, whereas a company with full-time employees is likely in a better position to have people go off the grid for a bit. That said, personally, even as a former contractor, I want NOTHING to do with work while I'm on vacation—to me, that's the entire point.