Have you ever noticed that basically all extant mid-range and high-end graphics cards support four display outs? Why has that become the standard? Who knows. It does seem to be the accepted configuration for the last few generations of GeForce and Radeon cards, though.
Vendors building graphics cards based on Intel’s Arc Alchemist GPUs could

Source: Hot Hardware – Intel Explains Mystery Of The Rare 5th Display Output On Arc Alchemist Graphics Cards