Earlier quoted context omitted.
Don’t 3D printed guns have a not insignificant chance of blowing the user up? Seems like a big commitment to using one.
No, actually, they don't. Typically the barrels are machined using electricity and the pressure-sensitive parts are hardened steel. Many firearms are made out of plastic anyway (Glocks, to name one you might be familiar with). It's not hard to build a reliable firearm with fairly little skill. In the United States, it's not even illegal to do so.
Point being: Yes they do, but also no they don't, because you're having different conversations about different types of weapons. Are fully plastic weapons commonly used for anything? Doesn't seem to be, and I would suspect the reason is because they'd be inclined to blow up/warp after a single fire.