Sony's UK boss right after E3 2013 said sales numbers during the first few months of the launch is crucial for the future of the platform. Majority of games don't get green lighted at third party publishers until they see the numbers. Sony struggled with this during PS3 launch due to the console's delay and Microsoft's head start (Hence not many games until MGS4 launch in 2008). Games that will be starting development right now, won't be released until 2-3 years later. If Sony can prove to third party publishers right now how well the platform is doing, they have an easier time securing exclusive content (without having to pay for them or much at all), or even just having priority of being the lead platform due to the bigger install base. It essentially keeps the momentum going for the long term and this is exactly why Microsoft was so strong during the first half of the xbox 360's life cycle.
5 out of the 10 games in JAN were sold the most on PS4. If Sony keeps this up, the exclusive partnerships being announced at E3 will be very interesting. EA has 3 titles(FIFA, Madden NFL, BF4) most sold on PS4. Even after Microsoft paid for NFL, BF4, and EA partnerships.