A huge chunk of low-level drug dealers are just struggling college students. I imagine if drugs were legal and taxed, they could be helped by some of that tax money going towards funding education.
Also, a lot of people go into illegal drug dealing because it is a high risk/high reward avenue, compared to many traditional prospects, where you can make a lot of money with comparatively little time investment. If I remember correctly, that was one of the stated reasons for why Notorious B.I.G. went into drug-dealing, despite being a good student and initially considering going to college for a more traditional high-education career.
Also, a lot of people go into illegal drug dealing because it is a high risk/high reward avenue, compared to many traditional prospects, where you can make a lot of money with comparatively little time investment. If I remember correctly, that was one of the stated reasons for why Notorious B.I.G. went into drug-dealing, despite being a good student and initially considering going to college for a more traditional high-education career.