An Apple article on EXS24 says:
"One of the changes to the EXS24 in Logic Pro/Express 8 is in the way it handles RAM. In previous versions, the EXS24 shared memory space with Logic, meaning that the total maximum RAM footprint for Logic and all instances of the EXS was a bit less than 4 GB. In Logic Pro/Express 8, the EXS24 addresses its own memory space. This means that EXS24 instances can use as much RAM as is available on the computer."
Why i.e. Spectrasonics plugs don't follow the same working philosopy?
This would cause many advantages for users who have large RAM on their computers (logic itself can address only 2.7 Gig + 3.9 VM)