You haven't been around firearms a long time have you? Just a guess mind you... not an insult.
You can take, say, ten M&P Smiths and line them up on a counter, and I would wager most would have a slightly different feel to their triggers. They are mass produced mechanical items and therefore, subject to imperfections of varying degrees. There is absolutely nothing wrong with someone who wants a particular gun because it suits his wants and needs at the time, but who wants to make some sort of change. Perhaps the sights are not to his liking. Or maybe there is an aftermarket recoil spring he wants to install. And then there is the trigger.
If you want to see wholesale discussions on trigger modifications, checkout Glock enthusiast websites, or 1911 websites. There are a multitude of aftermarket products for Glocks out there. Hell, just this past Monday, I had a set of Warren Tactical sights installed on my 3G Glock 19. And yes, I have made mods to that gun's trigger since I bought it. Also, my primary carry gun is one of my 3G Glock 23's and I have made three alterations to its trigger to suit my needs.
Not all brand new guns "need" a trigger job, but I contend that many people do, in fact, follow that path in order to get what THEY believe to be is best for them, be it target shooting, competition, or self defense. I am not going to defend what I did with my M&P40's trigger because of two reasons: 1) it's my property and I don't have to or need to defend my actions; 2) It has improved my M&P40's trigger to my satisfaction and that is reason enough for me.
Finally, a little piece of advice for you. You're comparatively new here on these boards and I suggest you may wish to consider your approach, presentation, and attitude towards others before you post. There are some very knowledgeable people on this site who will go out of their way to help other members with all sorts of questions and requests. How you come across may well dictate not only how you are perceived, but also how you are treated and responses you might receive. Just a suggestion.