traits during char creation

Little confused…
During nature question for elves our says replace or increase home trait with bitter or jaded…

Why wouldn’t i always choose to increase my trait As opposed to replacing it?

You can only increase the trait if you already have it and it’s being offered as a result of your answer. For instance, if you’re an elf from the Bustling Metropolis and choose Jaded as your home trait (rather than Tall), and then while answering your Nature questions decide that your heart has hardened in the long ages since the dawn, you may choose to increase Jaded to level 2.

Maybe your home trait wasn’t bitter or jaded, so you can only replace it? You can’t increase Bitter or Jaded if you don’t already have it.

If your home trait was Jaded 1, you can increase it to Jaded 2 or replace it with Bitter 1.
If your home trait was Bitter 1, you can increase it to Bitter 2 or replace it with Jaded 1.
If it was anything else, you can replace it with Jaded 1 or Bitter 1.