Why the sudden popularity of 12 inch arms

And, after upgrading to a 12" arm, the next step is linear tracking.

The advantage of 12 inch arms is nothing new, nor are their shortcomings.

And, after upgrading to a 12" arm, the next step is linear tracking

True

On paper a 12" arm is superior, but when it comes to manufacturing one it is not so easy. I think the combination of technical advancements, lowered manufacturing cost (or conversely the reduced aversion to a high cost arm), and the need to expand the product line (as others have said) are driving this. We are a fickle bunch so the desire to have the latest and greatest has a lot to do with it to.

Size does matter