I used to do the books for a small engine repair shop(chain saws, weed eaters, etc...), and people would always come in and drop their equipment off, then never come and get it, Sad fact is...with most machines it costs more for parts and labor than to just go get a new machine....I know that is not applicable with the higher end sewing machines, but a shop owner can't charge one person a deposit and not the next...they have to keep their practices even for all.
And....there are laws that are so prohibitive for a shop owner to get their money...in this state you have to store the item for a full year, and send out at least 3 certified letters asking for payment...and even then you have to go to court to get what is called a "contractor's lein"...to have permission to sell it...that means the shop owner has to take a half day off from the business, to go to court for what would eventually get him very little money anyway...
I don't blame any small business owner for charging a deposit...if you intend to retrieve your machine, you get it back anyway...