Originally Posted by
grant15clone 
Two Spool machines are cool. A spool of thread instead of a bobbin. I still don't know why this idea never caught on.
~G~
For the same reason they did not consolidate on needle size or shuttle.bobbin type. Too many options and no market pressure to conform.
(sorry if this looks weird, I don't know how to do more than one quote)
I suspect the cost of thread would have been a factor. Thread costs less per yard on large spools. I'm not sure the convenience of not having to wind bobbins would outweigh the in inconvenience of having to constantly purchase small spools of thread.
I've collected lots spools of different colored threads after finishing a project. They take up enough storage space, I'd hate to have double the amount.