One more reason in addition to what people have already mentioned that may be greatly overlooked:
It is generally illegal for foreign manufacturers to export such firearms to the US market.
They do not have enough points.
This means domestic US gun manufacturers have no foreign competition for such guns.
It is a market they own completely, and as a result it would be foolish not to provide a product for and encourage all possible growth in.
Here is the point system for semi-autos while revolvers have a completely different requirement system (provided by Glock through quick google search):
Characteristic Points
Length: for each 1/4" over 6" 1
Forged steel frame 15
Forged HTS alloy frame 20
Unloaded weight w/mag (per oz.) 1
.22 short and .25 auto 0
.22 LR and 7.65mm to .380 auto 3
9mm parabellum and over 10
Locked breech mechanism 5
Loaded chamber indicator 5
Grip safety 3
Magazine safety 5
Firing pin block or lock 10
External hammer 2
Double action 10
Drift adjustable target sight 5
Click adjustable target sight 10
Target grips 5
Target trigger 2
To be legally imported a gun must score 75 points or higher.
Several Glocks do not even qualify, and barely meet 75 points because they add special components removed after import:
- all models are imported with a cheap click-adjustable rear sight that is replaced at the factory with the stock sight
- target (grooved) trigger added to compacts & subcompacts
- target grips added to all models (required for the subcompacts)
Even with those additions the .380 Glocks simply cannot score enough points, as you see being 9mm and over gives 10 of the points.
Something like a Kel-tec P3AT or Ruger LCP could never possibly qualify for legal import.
For example let us see what a Ruger LCP would score:
Length: for each 1/4" over 6" 0
Forged steel frame 0
Forged HTS alloy frame 0
Unloaded weight w/mag (per oz.) about 10
.22 short and .25 auto 0
.22 LR and 7.65mm to .380 auto 0
9mm parabellum and over 0
Locked breech mechanism 5
Loaded chamber indicator 5
Grip safety 0
Magazine safety 0
Firing pin block or lock 10
External hammer 2 (?)
Double action 10
Drift adjustable target sight 0
Click adjustable target sight 0
Target grips 0
Target trigger 0
Total no more than 42.
The LCP would be illegal to import, and gaining another 33 points a nearly impossible feat.
The P3AT would score even worse.
Many blowback operated guns score even worse than them.
CCW intended firearms under 9mm in caliber are almost entirely restricted to domestic manufacture. Even those 9mm and over that are ultra compact are really hard to get to qualify.
Domestic producers do not have to compete with the rest of the world, their less expensive products, their cheaper foreign labor, or any of the other things that can typically give foreign companies an advantage.
This means this is a gold mine product for domestic gun manufacturers because it is something only they can easily provide.