the biggest factor is the lack of good titles for 3DS, so still some are still stick to NDSiXL (which now lowered the price, and some NDS Lite are now being lowered because it is now been stopped to produce), and still some prefer cheaper NDS rather than this, but who knows after E3 wee may found something good

maybe wee can expect to 3DS boom sale around June since that time they will release A+ titles (Ocarina of Time, Resident Evil Mercenaries)

but yeah some do not fond of 3D effect, but i still love my 3DS so far (im finishing shadow wars which is a better tactical rpg for today since its base in Xcom gameplay)

and by the way, i think Nintendo only lost around 100000+ nintendo sales forecast

@V1
ive seen in the 3D movies (which i mostly do watch no in the big screen now a days) that they do also use depths rather than pop outs, as some says that depths do less eye strains that pop out 3D effect