what do you mean by pure coco? You need to use coco croutons with coco coir - or else your plants will have wet feet and/or maybe a deficiency?
No, plenty of people use straight coco coir. Plenty of people also mix coir with perlite, or with coco chips (croutons) or with DE or with all 3. Some people mix coco with soil and everything else imaginable. There is no right way, there are personal preferences. The brand of coco coir you choose also plays a part in what works best for each person. For instance Canna coco might work great by itself right out of the bag while a 5kg block you have to hydrate might contain more too fine coir/ and sand (coffee ground appearence) that will accumulate at the bottom of your pot after many top feedings if you don't wash it away during hydrating.
No, plenty of people use straight coco coir. Plenty of people also mix coir with perlite, or with coco chips (croutons) or with DE or with all 3. Some people mix coco with soil and everything else imaginable. There is no right way, there are personal preferences. The brand of coco coir you choose also plays a part in what works best for each person. For instance Canna coco might work great by itself right out of the bag while a 5kg block you have to hydrate might contain more too fine coir/ and sand (coffee ground appearence) that will accumulate at the bottom of your pot after many top feedings if you don't wash it away during hydrating.