The Royal Computers YouTube channel explained why there is only one HDMI out of exits in the video cards, and the rest are Display Port.
Display Port itself is better than HDMI. He supports 16k, he has higher throughput, and also has the opportunity to connect monitors between each other. Perhaps that is why there are three such slots in video cards?

Not really. The real reason is in savings. The company that owns HDMI requires it to be paid with each video card sold with their port. At the same time, Display Port can be put absolutely free.