It is due to the fact that supplies of touch panels are limited that notebooks with touchscreen control features tend to be around $100-$200 more expensive than those without; therefore as a result customers are more inclined to purchase Windows 7 based notebook models in which touchscreen control features are not necessary.
Currently –according to Digitimes Research- touchscreen-based notebooks contributed to 0.5% of total notebook shipments at the end of 2012, however once touch panel supplies increase and become cheaper, the percentage is expected to increase to 10% in 2013.
While Windows 8 works perfectly fine using just a keyboard and a mouse, it does not deliver the new type of experience users expect from our touch-screen driven lifestyle these days. It is expected that the wide availability of affordable touch screen laptops and tablets will provide the significant boost in sales which have eluded Windows 8 so far.
Photo from: densitron.com