Thats only my examples. There are examples of multi-classing. What then? Class respec? There's also the arguement of skill allocation. 4 additional build points is not as easy at it seems. What happens after you eat a tome? Then the attribute cost more.
So its much easier just to do a reroll that covers it all if you can re-design the character from scratch.
>Are the reasons people give valid, or do they just like to constantly tweak their toons every way possible?
Both are valid reasons. Like I said before, what drives this game is character and builds. If you think character and builds are not important, then you're playing the wrong game.