There is one more area I think handspinning has a scalability issue: in the supply of materials.
There are custom spinning wheel manufacturers who have waiting lists that are years long. There are fleece producers who would need lead time to increase their flocks to meet greater demand. But in the meantime, there are production model spinning wheels and existing fiber available. We're not likely to experience an event like the seed companies had in the Spring of 2009 when so many people planted vegetable gardens and the companies ran out of stock.
Mostly what is scarce is the public's awareness that handspinning products are for sale.
Try filling in these blanks:
To buy clothes you go to the ____.
To buy food you go to the __________.
To buy a house you go to the office of a ____ ______ agent.
To buy a car you go to the ___ ___.
To buy a book you go to the _________.
To buy a spinning wheel you go to the __________________________.
I once heard someone explain what the place-name Pouce Coupe means, and how the meaning could be encapsulated in two words in the native language whereas in translation a lot more words would need to be added to make sense.
I run into a similar problem when people ask me where I buy my wool. Ask me where I buy food and I can tell you briefly. Ask me where I buy wool and I start hemming and hawing because I know I'll have to explain what Etsy is, tell you I have had conversations with shepherds you've never met, and warn you that you'll have to call ahead to a particular spinning supply store to make sure the owner is in. It's complicated to communicate where my sources are. There are so many and they must sound so far off the beaten track to anyone who doesn't spin.