The cost angle is real, but it's not the whole story - developers absolutely market it as premium, which lets them charge more while spending less. What gets glossed over is that exposed ducts and beams actually make apartments way louder and harder to heat evenly, plus they collect dust like crazy. I've seen plenty of people move out specifically because they couldn't control the temperature or deal with the noise from upstairs. It looks cool in photos and fits the whole "urban loft" branding, but functionally it's kind of a mess compared to traditional finished ceilings. The trend stuck because it's cheaper to build and easier to sell than because it's actually better to live in.