It is a combination of cost saving and marketing.
Cheap panels have low contrast, poor colour rendition, poor viewing angle (colour varies noticeably top-to-bottom), poor backlight design. Traditional panels use anti-glare coatings to convert pure reflections into lesser specular glare, but they cost money and with low end panels make contrast problems somewhat worse.
Marketing assume consumer laptops will be a few emails, lots of videos, lots of photographs. It is true that videos do look better on screens without anti-glare coatings, and by reducing internal reflections off anti-glare coatings it can improve blacks & contrast.
For office use they are diabolical, the idea you can "see through" the reflections goes against decades of research.
Basically you have to find an optimum balance between screen angle, lights & eyes - at the expense of comfort to the extent of becoming a contortionist! For some environments it is ok, with wall & office lights it can be very tiring.
That said, widescreen unless large and high resolution are equally a bit bizarre for office use - the extra width is useful in spreadsheets but the loss of height is problematic in office applications as well as aspect ratio (graphics).
The best laptop screens have IPS panels, but they were expensive and nearly always partnered with expensive graphics chips which with hindsight proved to result in short lived expensive laptops (ATi, nVidia etc chip & solder issues).