It can do. If weed was made legal here I would jump on it immediately; the only reason I don't currently is because it's too much of a hassle to find someone who sells it and I can trust. When I was in California with a friend they ordered some on an app and a guy pulled up in their parking lot twenty minutes later. That's legalisation bringing barriers to entry way down, which is a surefire way to increase popularity.
Not necessarily. Cannabis was extremely easy to find and there are reasons that something being banned would make it more exciting and popular. It's also gotten more expensive in many of the legal states.
In Illinois an ounce costs a solid $300+ at the stores.
Might be taxed at a really high rate, or production might be low. Took Colorado a long time for the prices to really go down, and it still varies a ton from city to city.
More popular and significantly less expensive, usually.