When /summon minecraft:skeleton
is used, the created skeleton has no bow; this was not the case in prior versions.
Affected mobs
Skeletons → No bow
Stray → No bow
Illusioner → No bow
Vex → No sword
Wither Skeleton → No sword
Zombie Pigman → No sword
Vindicator → No axe
Also produces weaponless strays and wither skeletons.
Also doesn't seem to do any randomization (never baby zombies, always white horse...)