Why? It's immunologically sensible : let the immune system train antibodies on a non lethal amount of novel protein antigen, like traditional vaccines, and (i bet to your point) in stark contrast with "homeopathy" in some definitions.
Homeopathy is way more extreme, for what it's worth. The idea is to keep diluting the thing until it's basically chemically absent, with only the "nature" or the juju or whatever it is.
Relevant Mitchell & Webb comedy sketch, title translated for Americans as "Homepathic ER".