As an executive vice president at Great American Group, a firm that helps liquidate the merchandise, clothing racks and mannequins at stores that are closing, Ryan Mulcunry has been watching booms and busts in the retail industry for almost two decades.

Companies like his have been busy in recent years, but lately one thing has been missing.

“In all the other cycles, including 2008, a lot of people would come in and buy racking, circular racks and so on,” Mr. Mulcunry said. “They’d buy it all and warehouse it and wait until somebody wanted to reopen a store and sell it back to them. Those people have gone away.”

He added, “People don’t think retail is going to grow again from a bricks-and-mortar perspective.”

As the internet continues to change shopping habits, stores across the United States continue to close. Less than halfway through April, American retailers have announced plans this year to shut 5,994 stores, exceeding the 5,854 announced in all of 2018, according to data from Coresight Research.

Retailers in good financial shape are paring locations as their leases expire, while brands like Payless ShoeSource and Charlotte Russe are filing for bankruptcy and shutting hundreds of stores within months. Payless and Gymboree — which both filed for bankruptcy this year for a second time — account for almost half of the announced closings.