You couldnt assume an intoxicated person would make the decision of using the phone or calling a taxi/uber. It is on the provider to do that, which is a 60 second process for a sober person to do.

Basically if they are intoxicated they are deemed to not be of sound mind and therefore you cannot assume that they would make a reasonable decision (such as calling a cab) to get home safely. Therefore the onus is on the provider to make that call.