Some character badly need knowledge points, but some are about complete for what they do.
Therefore the need need for KP varies from character to character.

You can indeed mouse over a craft to check what its reward are.
However having a direct value (based on your settings) for the craft by looking at the profit would be very nice.

Eventually there could be a different column for this specific valuation if profit needs to stay real profit.

Idea is that you could then tweak your settings and just craft whatever end up valued green (higher than zero)
Without having to double check every craft on every character.

For instance, if a craft only rewards you with sellable stuff, like a rune and some BoE finishing reagent.
In such case, there is no sens in crafting anything that is not showing at least zero or some profit.

Having everything factored into one value would save you the trouble of double checking every craft to be optimal.

the per character thing I understand but I am not quite getting the profit integration

Currently the kp cost setting assumes your maximum gold cost you want to pay for 1 kp

The profit integration allows you to directly see the overall value of a craft instead of having to check what the reward is.
That is, if you look at KP's case for instance, you don't need to check if a high cost craft contains a KP or not.
Because if it does and the KP value* is integrated into the profit, it will show a better value for the craft.

Idea is that in the CraftQueue you don't see the reward unless you mouse over to check the craft.
*What I mean by KP Value is considering the "Knowledge Point Max cost" as the set value for a KP.

This could be done using a checkbox like:
Integrate Max costs into profit [ ]