Our server has a skeleton spawner and after killing thousands of skeletons to test other issues with mob drops, I realized that not a single one has had armour or an enchanted bow, even before updating to 1.21.4 (we were in 1.21.3 previously).
MC-278731
Skeletons spawned from spawners never have armor or enchanted bows
Resolved
Cannot Reproduce
0
What is your world's difficulty set to? Mobs never spawn with armor or enchanted equipment if the difficulty is set to Easy, and it is rare to find mobs with armor or enchanted equipment on Normal difficulty, which becomes a bit more common the longer your world's chunks have been loaded. If your difficulty is set to Normal, how long have you been around that skeleton spawner?