Yes, no, maybe... it all depends. My my concealed carry and personal defense pieces I leave pretty much stock. These guns I view as tools. I may smooth up the stock trigger, ad a finger extension to a magazine on a subcompact or upgrade sites if I feel it would be helpful but I don't do 'bling' on these guns. I figure I wouldn't nickle plate my framing hammer so why dress up my 'work guns'. Besides, I'm not sure how that might play out in a court of law if I ever was involved in a shooting.
My target and hunting guns are a different story. I'll do mechanical mods. such as after market triggers, springs, sites or optics, even barrels to enhance performance. I also like to dress these guns up a bit with fancy stocks, etc.
So it all depends on what gun your talking about and it's intended use.