Otherwise people just shove their money under a mattress and the “inverted funnel system” collapses.

It’s actually because people would have to accept pay cuts from time to time, or companies would have to fire wholesale all or their people in a short time.

Also, rents would have to go down, debit could explode overnight… I’m not sure if people having a reason to invest is even an important enough reason to register.

Either way, none of that has any relation to capitalism, unless you count “any society that uses money” as “capitalism”.