@tylergrant said:

What companies offer these free shuttles?

They're not free, they range from $25-150 round trip depending on where you're coming from, they quality of bus and amenities. You can drink and smoke weed on any of them no problem and they bump good music. Bus To Show has always been my go to. Granted Bus To Show buses are school buses they're the cheapest option and pick up-drop off at various Cheba Hut locations which have bars.

Edit: I see the shuttles you mean, I believe the poster is talking about hotel-specific shuttles where you have a reservation.