Raw eggs contain the anti-nutrient avidin, a protein that binds to biotin, making it unavailable as vitamin. If you eat large quantities of raw egg you could theoretically become biotin deficient. Cooking destroys the avidin.
https://en.wikipedia.org/wiki/Avidin
Additionally, the protein in raw eggs is poorly absorbed, which could be because of other unidentified anti-nutrients. Again, cooking solves the problem: