I stay at SGS a lot and think that I may have asked for the butler once or twice in the 10+ years I've been staying there. When I want coffee, tea, etc., I push the "Guest Services" speed dial button on the phone (but it's delivered by the butler). Note that that button is on the phones in all guest rooms, regardless of whether or not you have butler service. I use the Concierge Desk as my primary point of contact for anything I need regardless of whether in or out of the hotel.

OTOH I stayed at StR Punta Mita and called the butler (well, the butler service operator, I guess) for whatever I needed. It seemed to work fine.