PS2 was hacked solely for piracy, GCN and Xbox actually for homebrew.
PSP was hacked cause Sony was dumb enough to allow kernel execution without any modification in FW 1.0 and 1.5.
The DS however saw the plague of piracy after the first gen flashcard that didn't need a GBA flashcard + bootcard/flashed firmware.
Once the R4 was cloned a billion times and prices where reduced to less then 5 quid per flashcard, piracy on the DS really took off.
Not to mention social media helped (people telling people they know etc)
The 3DS.. well.. it was inevitable, people already where waiting on a flashcard as they where familiar with the R4.
The Wii... I'm going to say that the minimalistic security did play a big part.
Other then that, the internet helped as well.
360 and PS3, well you got paid subscriptions and actual security.
Not to mention that hacked consoles (apart from PS3 and expensive XBL servers) don't have any online connection and the majority of the gamers want to play online all the time didn't help much with piracy.
Anyway tl;dr.
Nintendo's systems get hacked purely cause people where so familiar with the R4 and the lack of Nintendo's security (as well as a paid subscription and lack of agressive banning to prevents cheaters and pirates from accessing the online servers)