Veteran levels are good enough. They allow veterans with initially mediocre stats to eventually reach stat levels that would otherwise possible only for superb recruits. So there is much less stimulus to replace your veteran with recruit that has slightly better potential.
As for “Weapon Master – +5% chance to hit with all weapons” – you can already get +5% to hit with every weapon per 5 veteran levels (and also +5 to both defs).
