Rastafarians are vegetarian (not vegan) and pot smokers, so that may account for some correlation.
There are also people who wouldn’t consider themselves truly Rastafarian (which can be considered a religion, like any other), yet might be sympathetic to some of the tenets (like, for example, having dreads, eating well and smoking pot).
And there are people who have no connection to rasta who may engage in any of the three.
Dreading your hair has historically been a highly political act. People have gotten killed for it. Choosing to wear dreads means rejecting mainstream expectations about conformity and for some can be a very powerful statement. (Others do it because they think it’s cool.) Vegetarianism/veganism as well as pot smoking also have these aspects, so it’s understandable that there might be a correlation between them.
So in answer to your questions:
- Do dreads tend to be vegans?
No. The presence/influence of Rastafarians probably brings a corrrelation between dreads and vegetarians, and there is also a correlation because of people’s rejection of mainstream expectations (ie wear your hair like a white person, don’t smoke pot, eat what is put in front of you.)
- Do vegans generally embrace the dreads lifestyle?
Not at all. If we change “vegan” to “vegetarian” there would be more, but I would hypothesize that the “dread lifestyle” comes first.
- Do vegans typically smoke more pot than non-vegans?
Not at all, in my experience. The vegans and vegetarians I know smoke less pot than non-vegans.
I have met lots of people with dreads, lots of pot smokers, and lots of vegans, yet I don’t think I know a single person who has all three characteristics. To the OP: have you asked this of the people you know who have all three characteristics? If you don’t know any, then from where comes the stereotype?