All men are bachelors at some point in their lives. Except, I suppose, those of cultures in which boys are matched from birth to a picked bride. Bars or taverns used to be places pretty much restricted to men, though women eventually broke through that barrier. Today, singles of either sex can go to a bar alone, though there are some where no respectable woman would want to go. The idea of a bachelor is a little solemn.
I recently saw again the movie Anatomy of a Murder, made from Robert Traver's (John D. Voelker) novel of the same name. In it, the defense attorney, Paul Biegler, is played by Jimmy Stewart. Biegler is a bachelor, who enjoys fly-fishing, talking the law and sipping whisky far into the night with his alcoholic x-attorney Parnell McCarthy, and playing jazz on an old upright piano. He isn't married, and there's no reference--at least in the movie--to his ever having been married, or having any plans to be.
A bachelor, like any single person, may become slightly eccentric in his ways, since he has no one to moderate his habits or interests. It may be that people who are single are just not the marrying type, or they've tried it and failed (divorce). Solitary drinkers may become drunks, without a woman around to keep them honest.
Anyway, I like to think of a bachelor as one who might like a drink like this one, a little seductive, but proper, and serious, like a well-pressed grey suit. Straightforward and relaxed, with an orderly structure. A drink you could have over and over, not cloying or flamboyant. I haven't been a bachelor for almost 44 years.
Swirled around in a cocktail shaker with ice, and poured up.
4 parts rye
1 part praline liqueur
1 part triple sec
1/4 part amaro
dash of herbsaint
dash of Angostura bitters