Because for now it is the only one that has all that features combined:
- 4k resolution
- 144Hz frequency, for showing up to 144 images per second
- Nvidia G-Sync, for rpeventing tearing
Tearing example - HDR, for increased contrast
In case it is too expensive, I recommend looking for a monitor with the same features but lower frequency. The difference betweeen 144Hz and 120Hz should be almost indistinguishable.