Well it's what was available at the time. Modern TFTs had not been invented yet, and the first time I saw a 386sx laptop with a passive matrix monochrome display I thought it was so amazing that a whole computer could fit into something I could hold in my hands. The plasma screens were very expensive and only came on high end machines. The first active matrix color LCDs cost even more, a laptop with one of those was around $4,000 more than one with a passive mono display. On top of that, the color displays were smaller and almost always had at least one dead pixel. The vast majority of laptops on the market had passive matrix displays, even up into the early 2000's.