Because it is a healthier platform in the long run. PS2 proved the point that with 3rd party support, you don't need a lot of exclusives to do well. The games people care more are 3rd party titles, like we had CoD, BF and GTA being kings in the previous gen. This gen we will start to see an early domination with Destiny. These games have heavy advertising and are capable of creating hype. People will by a console to play them and they will choose between PS4 and X1.
X1 will cover a lot of terrain to close the gap during the holidays because GTA V, AC and Destiny will help him do it. Of course, more people are choosing the PS4, but there is enough people choosing X1. A console has to be made for 3rd parties, not by your studios. Nintendo has its marketing budget, but Sony and MS count on their marketing budgets and the marketing budgets off all companies making games for them. And people will buy what the ads them them to buy.
I see you prediction on the sig. Why the PS4 will do worse than the PS3? Why a record selling console will fail to beat a troubled predecessor that was launched at US$ 600 and made mistakes from 2007-2010 non-stop? Why the X1 will only outsell the Wii U by 5M when it simply crushed the 1 year advantage and it's close to passing it right now? Why the Wii U will sell 35M when it is tracking behind the GC that only did 21M? Unfortunately, these predictions aren't making any kind of sense.
Despite all that, predicting the 3DS ending with more sales than the PS4 at this point is plain craziness. 3DS and Vita are facing direct competitions with smartphones. The consoles aren't. Why would they? Playing CoD in a 40' screen with 30 people looks any kind of similar to playing on a 5' tiny screen with garbage touch control? Just the kind of hate the Dualshock 3 got for not being as goos as the 360 controller for shooter shows that the public can be quite picky. PS4 will have legs as all its predecessors had. At this point, PS4 may even end outselling Wii U + 3DS, but that's a bit of a stretch. PS4 is actually looking to do around halfway the distance between the PS1 and PS2 and end with 120M. X1? You could get the total numbers for PS360 and transfer some sales to PS4 and maybe add the natural market growth.
