O nce a simple (often rowdy) night out with friends, bachelor and bachelorette parties have turned into lavish affairs more akin to luxury vacations, often requiring flights, accommodation, pre-booked activities — and even multiple, matching, on-theme outfits.

Brides and grooms-to-be are renting villas on Caribbean islands, chartering yachts and planning spa weekends at luxury wellness resorts frequented by movie stars.

Celebrities are leading the charge. Lauren Sánchez celebrated her bachelorette, ahead of her wedding to Amazon billionaire Jeff Bezos, with a slew of A-listers on a Parisian getaway. Selena Gomez hired a yacht and a mariachi band in Cabo San Lucas, Mexico.…