Well, PSO2 is a character progression game, no? You may not "need" anything, but the point of games like PSO2 is to always get stronger and better, whether that's through gear or skill.
The actual content, while important, is generally not the main draw of games like PSO2 and is more a vehicle for the overall gameplay loop.
People wanting to max things out by using all the systems available to them is quite normal, and people should be encouraged to do so. It enhances the gameplay loop by making more things worth doing (especially when it comes to augments), and always giving you some sort of thing you can do to become stronger.
If you were to ignore the affixing system in PSO2, you would run out of things to do extremely quickly.