Snakebites are a bit of an edge case: the production of antivenoms essentially involves inducing an immune response (in a convenient, usually large, animal) and then extracting and purifying the neutralizing protein produced. So, it is very much the case that you can prime an immune system to recognize and respond to venom.
The trouble is that snakes tend to (in the case of actually dangerous snakebites, a dry strike is just a couple of puncture wounds) introduce a substantial amount of venom into the wound, and the venoms frequently kill (or cause nasty localized tissue destruction, there are lots and lots of neat variations) substantially faster than the human immune system can synthesize the necessary counteragent, even if the person has prior exposure.
An antivenom has the advantage of being a relatively massive amount of the correct counteragent, ready to be injected into the bloodstream faster than you could synthesize it yourself.
For the less dangerous venoms, and the lower-volume strikes, acquired immunity is more useful.