it's true you can make blowback design in any caliber but why would you? As you said the weight of the slide and the spring strength would have to be enough to keep the slide in place until the bullet leaves the barrel. It can be dangerous if the slide begins to move back prematurely.You know, as often as I have seen this argument, I cannot understand it for the life of me.
Based on similar reasoning, there's no reason to own a 9mm.
.380 ACP pistols are generally smaller, lighter, easier to concealed carry, and in some cases are easier to rack the slide on or have less felt recoil.
If more power is deemed necessary, then there are firearms of similar (sometimes equal) size and weight in .40 S&W, which is a bigger, heavier bullet which delivers more energy compared to 9mm Luger. In addition, .40cal pistols are typically much cheaper than their 9mm counterparts ever since the FBI dropped the cartridge, and ammo is only marginally more expensive. Last but not least, modern .40cal pistols which have been designed specifically for the .40 S&W cartridge will hold up to a steady diet of ammo far better than a 9mm pistol will hold up to a steady diet of +P/NATO Spec ammo, and firearms which have been properly modified to handle .40 will hold up just as well as their 9mm counterparts.
The Hi-Point C9 is a straight blowback operated 9mm Pistol. Historically, the H&K VP70 was also straight blowback. It's entirely possible to make straight blowback 9mm pistols or even .40s/.45s, it simply isn't done very often because the weight of the slide and recoil spring have to be excessively heavy for it to function reliably.
There have also been many straight blowback operated SMGs, Carbines, and Rifles in the past as well.