How come they used to tell you to turn your cell phone off at the hospital? why is this no longer than case? even doctors use them now

Good observation: I do not know if there was a specific reason and different facilities may have different rules and regulations, but my guess is that it had to do with 2 things: failure to enforce the rule and demand, supported by the fact that the extra noise would not make a difference due to the baseline noise level. For caregivers the need for real time two-way communication may explain it.