Access to the diamond and concierge lounges is strictly controlled and only those authorized to use them may enter. It isn't as though any passenger can wander in for the complimentary drinks and snacks. Concierge lounges are reserved for those in Grand Suites or higher, and diamond plus Crown & Anchor members. The Diamond lounges are reserved for diamond and diamond plus members only.
Art auctions will provide complimentary glasses of cheap champagne - up to a point. If you aren't actively bidding or otherwise showing interest you'll find yourself cut off quickly.
Wine tastings on Royal Caribbean are not free for everyone. Higher level Crown & Anchor members might get a coupon for free entry, but otherwise they have a cover charge.
I've never known any ship's bar to offer free drinks other than at welcome aboard receptions and other special events.