I don’t think we have a term for people who quietly keep a well stocked pantry, have a water setup, garden, have hobbies like canning, etc. That’s just being a bit rustic/prudent I guess. So then, the “prepper” derogatory label is only applied to the people who do it in the action movie/silly way. But, the question of how prevalent they are is a good one…

The term you're looking for is "homesteader"