I think they were used more in the past than today - I’m not sure, it’s just a hunch.
Cricut and other cricut like machines have replaced stencils in many homes.
For crafters they are game changing.
My wife and daughter both make class shirts each year. No expensive scissors could cut the patterns of iron on vinyl that the cricut cuts.

Cricut home stencil cutting machines have revolutionized the crafting world. It isn't just about the cutting. It's about the intricate DESIGNS one can cut now:
It's not just for flat crafts. Paper flowers shapes were all cut out, layered and rolled into flowers:
Ooh! A Tiana 3-D princess shadow box:
Adhesive backed heat transfer vinyl can be heated and applied to travel mugs, T-shirts, and other items and is very resistant to coming off. (The top left one is etched with an acid solution.) Whole home businesses are successfully selling personalized items:
One year, in one of the Facebook stencil groups, they found blank canvas tote bags on clearance at Target for like $6 - $10. Everyone bought as many as they could find, added a stenciled design out of the heat transfer vinyl, or fabric painted different designs on. Some took custom orders for personalized bags. Then they sold the decorated totes for $30+.
For crafters who can draw, there is software to create their own designs and cut them out. Then they can layer them together on a piece for more intricate designs. And they can replicate the designs over and over on new items than doing it all by hand.
There are stencil designers who sell their digital stencil patterns for people download and cut at home on their machines. This designer, Jennifer Maker,
gives away all her intricate 3-D stencil cut files. She also allows people to sell their finished items. She makes money by posting affiliate links to buy the supplies to make the crafts from Amazon. For instance, one would need to buy the heavyweight cardstock paper and the LED puck light to make these tree lanterns. She must do really, really well, as she has over 600+ free intricate patterns posted.
Sorry, I got carried away.

The possibilities of what to do with stencils are endless now.