Many reasons, actually.
1. All ps home consoles have been positive experiences for consumers. The insane support that the ps3 got over the years and especially last year at the expense of ps4 gives potential buyers a reason to trust Sony. The wii and psp left consumers disappointed, hence the consoles' low sales.
2. Does not have strong competition. Ms fucked up and Ninty stood no chance with the dudebros/ cool teenagers-young adults. Whatever people say here, the general public does see Ninty as a company for kids. It's simply not cool to own a wiiu console. Wii was successful entirely because of the motion controllers and their appeal is at the moment gone.
3. Everyone loves an underdog. The worse Sony was/is doing as a company the more fanatic it makes its fans. They worship the company to no end, because they see it as the good guys fighting a greedy big company (ms has a bad image-not my personal view). They bought it day 1 to support the company and to show their opposition to ms.
4. Good initial sales created hype. The ps4 has been everywhere. Facebook (people talking about it), 9gag etc. It has a good image and it's considered a hot item at the moment. People buy it because they are influenced by others, not because they really want or need it. Shortages have only increased the hype. There are so may reports/forum threads about shortages that it makes feel like they achieved something buy buying one (as if they won a decent amount of money from a lottery ticket).
