Actually, LED screen projection rooms have existed for several years now, but adoption has been slow. Personally, I think that given the current state of LED technology, replacing traditional projection cinemas is still not feasible. There's a lot of hype online about LED cinema screens, so let me talk about their disadvantages.
One disadvantage of LED cinema screens compared to projectors is that the clarity drops significantly at different viewing distances. Optical projection pixels are almost perfectly aligned, but with our company's small-pitch LED screen (P0.9), it looks quite clear at four or five meters, but at three meters, it's just a jumble of square pixels, like a mosaic. It's like paying for infantry to watch a cavalry movie.
Another issue is resolution. To achieve 4K resolution, you need to consider the screen's physical size, which essentially limits the LED spacing. These two conditions mean the spacing of LED cinema screens can't be too small. Are the first few rows of viewers paying to count how many LEDs there are? Although each module of a cinema screen undergoes color calibration at the factory, and there shouldn't be any noticeable color differences between units from the same batch...
The problem is, suppose you buy this screen and use it for a year. Then one day, some LEDs on one module suddenly stop working. The replacement module from the manufacturer is brand new, but its brightness will be noticeably different from the rest of your year-old screen. While this difference can be corrected with calibration, you'll gradually find that from the moment the first dead pixel appears, you might be calling the manufacturer daily to replace modules and calibrate the colors.
Furthermore, let's compare this. I haven't seen the inside of a movie projector, so I don't know how many light sources a cinema projector has—let's say five. If one light source fails, you just call someone to replace it. But what about an LED cinema screen? Let's say it's 4K resolution—that has over 8 million LEDs! Is it more likely that one out of five LEDs will fail, or one out of 8 million?