Oh boy, strap in folks, this gets bumpy.
We cruised the BVI a year ago spending 6 months onboard and have had dinners, lunches and sundowners from Jost to VG to Anegada and everywhere in between. The service charge as I understand it was a tip - plain and simple, to even out the playing field. North Americans typically leave a gratuity, some European visitors, not so much.
That said, the automatic addition of a 15% surcharge, call it what you will, has driven, the "service" provided in the vast majority of places in the BVI into the dumpster.

Exhibit A - Pirates Bight on Norman, we were asked "What d'you wanna eat?" by the person taking our order, cannot call her a server by any means. Food was mediocre at best, literally dropped on the placemats, she could not have cared less, and for just showing up, expected the 15% mordida to be paid.
I asked for it to be removed, and was prepared to politely explain to the manager on duty why it wasn't warranted. She came back, said it was off, dropped the bill on the table and walked away. No explanation asked for and therefore none offered. I'll go back to Pirates, they have pretty good WiFi, but that's it. I have beer on my boat.

Exhibit B - Village Cay Marina restaurant. The "Local Honey-Stung chicken" ($14.95 USD) is available in the same pre-pack (one skinny breast, a leg, a thigh and wing) in the frozen food bin at Riteway for $4.95 a bag, limp frozen chips not included. Really guys?

A great number of these establishments have a captive clientele - charter guests who want a cold beer, are will accept overpriced and underwhelming food with below par service - because its very likely they'll NEVER BE BACK - so as a server, I'm just mailing it in, I'm still getting my slice of the 15%.
When service warrants it, I'm a damn good tipper - 20 - 25, even 30% if my socks have been blown off. Otherwise, a big bag of nope.
Spare me the 'oh its how they make a living' discussion, it takes little if any effort to provide decent service to people and maybe, just maybe the word will get out about how great the food and service really are. If we continue to accept mediocre service, this will become the benchmark going forward.
Need an example? Go see my buddy Ratty up at the Fat Virgin Cafe in Leverick Bay. Their roti is worth the trip on its own. He GETS it, and from what I understand, makes out pretty good with the tip jar.
</rant> and thank you for your time.