Hatchets and throwing knives/hatchets are extremely rare for some reason. Which doesn't make sense as these weapon should be quite appealing to raider types and fits their popular image.
The hatchet is in the same tier as tire iron, but it should be a bit less common since it's more powerful and tire irons probably were much more common in pre-war times.
Throwing knives and throwing hatchets should get similar treatment, it's especially fitting to make sadistic raiders like the Fiends, Jackals and Vipers use them while these weapons wouldn't be used by Powder Gangers since these guys are more into explosives and wouldn't have much access to these weapons anyway.
It also makes the Cowboy perk more appealing for melee characters as these weapons are pretty powerful with a 25% dmg boost. It also makes acquiring them much less of a hassle since you won't have to buy them from Mick & Ralph only after passing a speech check, you won't also have to rely on sheer luck just to get the hatchets.