Apple doesn't ship stuff just because it's available; there has to be some appreciable value.

Faster refresh doesn't necessarily mean a better display. I suspect Apple's displays are higher quality than most competitors even if they max out at 120Hz.

Here are the specs for the latest MacBook Pros:

    16.2-inch (diagonal) Liquid Retina XDR display;1 3456-by-2234 native 
    resolution at 254 pixels per inch
 
    XDR (Extreme Dynamic Range)

    1,000,000:1 contrast ratio
    XDR brightness: 1000 nits sustained full-screen, 1600 nits peak2 (HDR content only)
    SDR brightness: 500 nits


    1 billion colors
    Wide color (P3)
    True Tone technology
    Refresh rates

    ProMotion technology for adaptive refresh rates up to 120Hz
    Fixed refresh rates: 47.95Hz, 48.00Hz, 50.00Hz, 59.94Hz, 60.00Hz