Because most people don't want a 48"+ """monitor""" on our desks. Some people value their neck muscles, ligaments and bones, and and prioritize ergonomics and physical comfort.
For a long time I saw people with 2 or 3 monitors on their desk. They worked like this since the company offered multiple monitors until retirement, the physical actives ones didn't complain about comfort, but usually they had good posture, the sedentary ones...
Because I don’t want a huge TV in front of my eyes on my table and get blinded by it? That’s not even viable or suitable. Also this is faster and optimized for gaming and has no burn in.
What's the difference between one big display and multiple monitors? I'm more blinded by a small (24"/27") LED monitor than a 48 inch OLED.
You can buy an arm monitor if you don't want to use the space on your desk and also put the monitor further away from you. I have it on my standing desk and I still have have enough space.
I'm using 48CX for a year an half and there's no burn in, I usually play one game, browse and netflix. In some countries you can buy extra warranty to cover the burn in.
Initially, I was hesitant to buy it, but I said what the heck and bought it, I haven't regretted the decision. On the contrary, I asked myself why I hesitated for so long.
Like
@Valantar wrote, is a matter of taste, maybe you don't want a big "monitor" on your desk.