You don't 'need' them, but you might like them. Without them just leave a plastic retaining button out of trunk liner each side and you can pull it back and reach adjusters, but these let you drill a very small hole in trunk liner and have the adjuster right there.
I have mixed feelings about these remote adjusters. Placing one on the drivers-side through the fuel lines is immensely helpful. However, placing one on the passenger side had poor results. If you have a spare tire in your trunk the remote adjuster sticks up too high out of the shock mounting point and presses up against the tire. This pinched the top of the remote adjuster causing the adjustment line to shear off when attempting to use it. Admittedly, you could run the remote adjuster without a spare tire, but these products are aimed at people who want to keep their trunk configuration intact. I ended up putting the normal adjuster back on and that worked fine. I would like to see these sold individually for NA owners.