To be fair - some distros are moving away from GRUB as the default.
Pop!Os uses systemd-boot (formerly gummi-boot) by default if you're on an UEFI system, and only falls back to GRUB for legacy bios.
Arch is also much easier to setup on systemd-boot.
The issue is that GRUB still has a very compelling support matrix - it'll work basically everywhere, and with most all configurations. So if you're already running a batteries included distro, where someone else is doing most of the configuration and the downstream systems are hugely variable (old consumer hardware) - then GRUB still makes the most sense.
Pop!Os uses systemd-boot (formerly gummi-boot) by default if you're on an UEFI system, and only falls back to GRUB for legacy bios.
Arch is also much easier to setup on systemd-boot.
The issue is that GRUB still has a very compelling support matrix - it'll work basically everywhere, and with most all configurations. So if you're already running a batteries included distro, where someone else is doing most of the configuration and the downstream systems are hugely variable (old consumer hardware) - then GRUB still makes the most sense.