Wizards lack objects to store great quantities of mana. To store a large quantity of mana one needs animus, and animus is found around life. The more experienced and intelligent the lifeform the better. People however don’t like enslaving the souls of others solely to make better items, however egoswords are somewhat tolerated, provided they gave consent.
Blood magic is the most powerful. By that I mean if you wish for a truly devastating spell or item, you need to sacrifice something, so either you sacrifice yourself, which is commended, or you sacrifice others, which is reviled. A pragmatist would do the later on a field of battle. A hero or fanatic would do the former. Pragmatist are more numerous, but fanatics are more tolerated. It’s just difficult to collect and retain animus as it often naturally tries to disperse once removed from its body.
Certain items can channel and retain mana better than others, but animus could still improve these, so it’s relative.