The high res textures are availible on the PC because higher end PCs can handle them. Lower spec Pcs are reported to be struggling, how do you think the consoles with their fixed hardware specs equivilant to a low-to-mid spec PC are going to handle them? Especially as it seems the game is already puching the limits of what the consoles are capable of.
Because their graphic cards can't handle it, pure and simple. There are plenty of PC users with sub par set ups that can't use them either. If the consoles could have used them without hitch you can bet your [censored] they would have been in the game already and not additional content.
Yep, I'm able to run the basic game on high settings but my graphics card can't handle the hi res pack. This is why it wasn't released as part of the basic game, consoles and many PCs can't handle it.