As inane as post #1 is, OP brings up an interesting topic.
No one need to upgrade their bikes.
The only function-based reason I can think of to alter one's bike is having a problem or dislike of the bike's current functionality, e.g. one's bike's fit, gearing, tire shock absorbency, wheel durability, etc. Something that can be radically altered.
Otherwise, it's just a matter of throwing money at the bike because one obsesses over it, e.g. upgrading to a new gruppo with the same shifter functionality and gearing, wanting a composite seatpost- don't tell me that new post actually "absorbs shock", getting more expensive tire of the same width and run at the same pressure.
I'm talking about the changes which bring benefits which many people are skeptical of.