Glocks, M1911s, and a few other handguns have a huge aftermarket available. The sky is the limit for what you can change, and modify on some pistols. Of course the problem is that not everyone is a gunsmith, competent, or even has average intelligence. Just because an aftermarket part is available does not mean that it will work, or is an improvement. It's kind of humorous that the guys that cannot even change their own oil feel comfortable doing mods on their weapons.
When "Bubba" works on a firearm, it's often unsafe, unreliable, and often unreasonably fugly.
Sometimes it's a good idea to remember, "Just because you can, doesn't mean you should."