Why Do Some Airlines Still Operate 4-Engine Jets?

The question about why some airlines operate quad-engined commercial airliners is mostly a legacy question. No commercial quad-engined passenger aircraft are produced today, and there are no concrete plans to bring them back, apart from the supersonic Boom Overture. Barring Russia producing more obsolete quad-engined Il-96 passenger jets, the last passenger quad-jets were delivered in 2021 as Emirates received the last Airbus A380.