seems like every time i buy a pistol i like you always have to buy something to make it better.
No - you don't. If you're satisfied with the gun's performance out of the box, then there is no reason to change anything
However, not all guns are the best they can be from the manufacturer for everyone.
As an example, I bought a S&W Model 625 Jerry Miculek revolver that was supposed to be put together by the S&W Custom Shop. I didn't personally like several things about the gun and had them fixed to meet MY requirements for the gun.
Both the double action and single action trigger pulls were atrocious at 10.5 lbs DA and 9 lbs SA. With some work, the trigger is now 7.5 lbs DA and 5.0 lbs SA.
The cylinder's chambers were not chamfered making loading the gun with the moon clips difficult as you had to vigorously wiggle the loaded clip as you pushed it toward the cylinder. The chamfered chambers make the gun load far easier with just a push as the bullets self-center over the chambers.
Lastly, the crown on the barrel looked like it was done with a chop saw and I had the barrel squared and crowned properly.
Would the gun work without all of the modifications? Sure. Would it work the way I wanted it to work? No. I fixed it to meet MY requirements.
On the other hand, some guns need no improvement for my use. My SIG P229, P938, HK P30 & VP9, Springfield EMP and several 1911's are still stock as delivered by the manufacturer as they work fine for my use.
The flip side to that is my FN SLP shotgun. It has had extensive work done by SRM Performance and works much better than it did when stock from the manufacturer.
That's all many people are doing with their guns - making them work the way they want them to work.
There is no requirement to modify a gun unless there is something you feel could be improved for your use. If there is - fix it if you choose. If not - leave it alone