If I own 300 EUR worth of coin out of a supply worth billions or even trillions of EUR, I'm just not ever going to bother staking it.
In NXT you don't need to stake with active connection or online machine. You can lease your account to other address, maybe to some developers or whoever. At the same time you can spend your NXT when and wherever you like.
See above, search for delegated staking.
Concentrating stake like that does not make it more secure. It just creates a central point of control or potential compromise (custodial risk with respect to staking as described by monsterer is the same here, in fact worse because people are more likely to concentrate stake with centralized entities if their coins can't also be stolen).