Whenever I mention that I carry Glock pistols, I am asked what sort of modifications I have done to them - sights, trigger, grip reductions, and so on. When I say that my Glocks are entirely stock, more questions follow - most relating to the word "why."
Glocks are similar to AR-15s in terms of popularity, and the number of companies offering every part imaginable for both platforms are too numerous to count. Many of these parts are intended to make the firearm more practical for real-world use, or so say the advertising claims. This practical parts plethora puts plenty of pressure on pistol people. It's not quite at the level of "I don't have the new flux capacitor assembly from 3rd Millennium Blasterwielder, this means I'll get killed in a gunfight," but the atmosphere in the firearm community often overemphasizes the importance of minutiae gear considerations.
The primary reason why I leave my Glocks alone is that they are functional and reliable as-is. Not all Glocks are, and I am rapidly losing faith in Glock's ability to do the right thing, but vintage Glock 19 Gen 3s and newer production Glock 22 Gen 4s are generally reliable pistols. In the absence of a clearly identifiable need for modifications, I do not wake up every morning trying to think of new ways to spend money.
Furthermore, I have respect for the engineering expertise of firearm designers at major manufacturers. No, they don't always get it right, and yes, they often have to design firearms with illogical legal or liability concerns in mind. However, they have the resources to thoroughly test designs before releasing them to market, and recognize the concept of manufacturing the pistol as a system better than smaller companies which seek to modify specific portions of the firearm.
Those who take a myopic view of trigger modifications, for example, often render firearms unreliable (light strikes, failure or inability to reset) or dangerous (disabling or reducing the effectiveness of internal safety mechanisms). This is not to say that all trigger-related modifications are bad - magazine disconnects, for example, are dumb. However, if something sounds too good to be true, such as a 1911-like trigger in a Glock, then it most likely is (I have two requirements for a carry firearm - that it work when I want it to, and that it not randomly shoot my balls off when I'm running, jumping, and climbing trees).
As with any industry, a number of companies seek the endorsement of celebrities in order to sell their products. In some cases, the celebrity or personality recognizes the responsibility of this and tests, examines, or evaluates the product in a proper manner - or seeks input from others who may have engineering expertise - on the product before endorsing it. In other cases, names have been attached to products that should not have been released to the general public as-is. I am no celebrity, but at this point I can tell the difference between a genuine T&E offer from a manufacturer and someone that just wants to give me free stuff in exchange for pimping it on my blog.
Before anyone asks about other pistols that I carry from time to time - my Kimbers are far from stock. This is because Kimber didn't design the 1911 - they just found ways to screw it up. My J-frame has a Crimson Trace lasergrip. The Kel-Tec P3AT is stock with the exception of a..."custom finish." The Sigs and Berettas are stock. Kahrs are stock. Oh - I used to replace Glock sights before they switched to using a screw to attach the front sight.
Now, if you want to modify your carry guns, feel free to do so. Whatever works for you should work for you. What works for me might not work for you. And as a final note, I do not put much stock in the idea that modifications to carry weapons might be used against a concealed carrier in court. If the shooting is justified, little else should matter.