It's because this generation of consoles are all fairly inexpensive, and as a result underpowered. Sony got their fingers burned in the PS3 era by releasing high end tech at a premium price. People simply couldn't afford it or wanted to see a slew of games and a price cut before they bought one. This time around the PS4 came in a nearly half the price in my home country.
I personally would prefer a top end more expensive console that was up to scratch against high end PC's. Think about it, you only buy a console every 5-7 years and the same people bitching about $900 AUD PS3's are the same people who buy a $700 AUD iPhone EVERY YEAR, and the new model has only slight improvements.
This generation of console clearly had a set price cap in mind when they were designed, maybe because of the amazing success of Wii with underpowered and inexpensive tech?