Why do they always take games off console and dump them on PC and not optimize them?

While it varies by developer & publisher, the main reason why PC ports of console games generally aren't optimized is because there's WAY TOO FREAKING MANY POSSIBLE PC CONFIGURATIONS TO DEAL WITH!!!

When I say "TOO FREAKING MANY", I'm talking about the range of PC's running the same OS...  which can anywhere from a potato chip (stuff that can barely run the OS itself) to supercomputers (that can run almost anything) to GLaDOS (who managed to go from a Supercomputer AI to potato & back to Supercomputer).

Developers have to pick their battles here by reviewing their game as a whole & then consider what segment of the PC computing range to focus on (by setting minimum requirements & then recommended requirements) & go from there.  After getting the game to work their selected range, they can THEN start working on optimization & bug fixes.

For game consoles, developers only have to deal with roughly 2 - 4 hardware configurations (excluding storage space)...  so they smaller configuration window to make their game work in, but that restriction also forces them to optimize the game to fit within that window (to hit that "working" state).

Beyond that, it's more a question on how much time & resources the developer wants to put into optimization.  Smaller teams may not have the resources to do so as they want to move onto their next game project while other, larger teams may leave a small contingent of staff to handle optimization.

Optimize to what?  There are millions of possible ways a PC can be built.  They can't optimize all of them.

PC's have been vastly superior to any game console for many years, and will always be so in the future, and so there will always be profits to be made because of it.  Some money is better than nothing and it's usually more profitable to follow console trends that target those consumers.