Vita and Wii U have no major new software releases and neither are being advertised well.
Who in the seven circles of hell expects them to sell well?
The sales are terrible, yes, but without software support people won't buy new systems. Nintendo might have announced some games, but they've given no signal as to when those games will be available. That still leaves Wii U without a major release for the entirety of January and almost all of February, before three or four notable releases (but no major global blockbuster and no major first party title) hit the system.
Nintendo need to hurry up and announce dates for titles like Pikmin 3, Game & Wario, Wonderful 101. It's all well and good saying those titles are coming, but who is going to invest in a system when Nintendo won't even reveal what month those titles are coming out? Things will only get worse before those games are advertised and released.
Look at my sig. Plenty of people did.