It is how our brains are wired and a result of evolution. Even if a person lived in a paradise and had all their needs and wants provided; one of two things will occur - Either that person becomes bored or they wonder 'hmmm, I wonder if x,y or z could be better in some way?' and then trying to improve on perfection.
[1] Jebb, A.T., Tay, L., Diener, E. et al. Happiness, income satiation and turning points around the world. Nat Hum Behav 2, 33–38 (2018). https://doi.org/10.1038/s41562-017-0277-0
A more recent study was done on the "ideal salary point" and concluded that there really isn't one: https://www.pnas.org/doi/full/10.1073/pnas.2016976118
If humans could ever reach a state that would guarantee happiness we’d still be living in caves and having 10 children so 5 make it to adults.
Progress requires dissatisfaction with the status quo.