On some cruises you can get an "All Inclusive " ticket on the cheaper ships and the very expensive ones....take your pick....Neil's son Fala.
I can only answer for some cruise lines - P&O, Fred Olsen and Princess. No drinks are not included other than tea or coffee with meals. Some lines offer a wine package where you get a deal for about 6 bottles. As someone has already said it is usually only the very expensive cruise lines that include any drinks.
Yes, Seabourne offer Open bar: Complimentary wines, spirits, fine French champagne, soft drinks and mineral water. Silverseas will stock your in-suite bar. Just ask for what you'd like. The liquor comes in large standard bottles. When the original stock is exhausted, your cabin steward (ess) will restock, if not automatically, at your request. On champagne, Pommeroy is what they stock unless you order something else like Veuve Clicquot...Dom is extra.