COVID-19 is waning, but shopping for a Louis Vuitton bag, a Chanel suit or a pair of Gucci loafers increasingly means standing in line outside a boutique — and luxury brands have been conspicuously tight-lipped on why.

Most elite labels leaned into “appointment shopping” during the height of the pandemic, citing the need for social distancing. But as the threat from the virus recedes, some including Cartier and Harry Winston continue to impose the new policy.

They also have failed to convince shoppers and experts alike of their reasoning — if they bother to explain themselves at all. Major brands including Louis Vuitton, Chanel and Cartier didn’t respond to calls and emails from The Post about their persistent use of stanchions in front of store entrances, where queued-up shoppers are quizzed by “greeters” about prospective purchases before entering.

“We recommend booking an appointment prior to your boutique visit, as walk-ins may experience extended wait times,” Cartier’s website advises, without elaborating.

According to experts, roped-off customers can mostly thank a relentless epidemic of smash-and-grab robberies rather than social distancing for ramped-up crowd controls nationwide, including in New York, Chicago, Miami, San Francisco and Seattle. Theft got so bad last year that Beverly Hills hired two private security firms to patrol Rodeo Drive.

Meanwhile, at the Westchester Mall in White Plains, NY, where robbers ransacked a Louis Vuitton store in February, the boutique’s doors were closed, with stanchions inviting shoppers to queue up outside.

A pair of greeters wearing headsets — flanked by a pair of beefy mall security guards — asked customers whether they were there to pick up an order or to shop. Shoppers were let in only when an associate was ready to accompany them inside.

“They don’t want customers looking around the store without a store employee with them,” a sales associate told The Post. 

Luxury brands have managed to obscure the embarrassment of the situation partly because making it difficult to enter their stores “creates an aura of exclusivity,” says Steve Dennis, a Dallas-based retail consultant.

“Most of these stores aren’t crowded anyway,” and the lines are getting longer in states like Texas, “which didn’t particularly take COVID seriously,” said Dennis, author of “Remarkable Retail: How to Win & Keep Customers in the Age of Disruption.”

“The new nightclub, in its own weird way, is getting into a Dolce & Gabbana store on a Saturday,” adds luxury retail consultant Melanie Holland.

Last week, a Chanel executive provoked chatter when he disclosed in an interview that the company plans to open “private” boutiques in Asia next year for top clients. Chanel is hiring 3,500 new employees for the initiative, which experts say could be adopted in the US.

“Our biggest preoccupation is to protect our customers and in particular our pre-existing customers,” Chanel’s chief financial officer Philippe Blondiaux told Business of Fashion. “We’re going to invest in very protected boutiques to service clients in a very exclusive way.”

In response, fashion blog Highsnobiety questioned “What, exactly, do Blondiaux and Chanel want to ‘protect’ its customers from?”

Holland speculated that Chanel may be looking to keep its wealthy clients from becoming targets for thieves after they leave stores. But big spenders also aren’t typically walking in off the street, she adds.

“People who want to spend $25,000 for a small dress don’t want to stand in line,” Holland said. “Those customers are probably making an appointment with their personal shopper — they know that line isn’t meant for them.”

As previously reported by The Post, Madison Avenue boutiques on the Upper East Side in Manhattan including Chanel, Prada and Carolina Herrera are dimming their lights, locking their doors, and opening by appointment only in a bid to deter a wave of brazen daytime shoplifters that have terrorized the glitzy thoroughfare this year.

In February, a team of seven thieves strolled out of The Real Real on Madison at 71st Street with nearly $500,000 worth of handbags and jewelry.

In the wake of such heists, there is simply a “new lack of trust” on the part of retailers “about who is walking through their doors,” said Susan Scafidi, founder and director of the Fashion Law Institute at Fordham Law School.

In practice, most luxury brands assign a sales associate to each customer or group. The days of walking into an exclusive boutique and “browsing” without an associate shadowing you are largely over, said one sales rep.

Meanwhile, staffers at upscale boutiques including Chanel, Gucci and Burberry are being armed with talking points for inquisitive customers, some of which sound plausible.

“We are still dealing with shipping delays from Paris and you don’t want everyone to come in and to notice that the store doesn’t have the latest styles,” a sales associate at a boutique operated by a major luxury label told The Post, speaking on the condition of anonymity.

“You want to be able to tell them one-on-one that the pieces are on the way,” the associate added.