pressing exit button task remain active in memory

Hy to all

in my i8910HD (sw: XXII2 - custom sw:OITVIJ1)
when i press the exit button,
for example when i exit from message or address book, the taskremains still in memory:

launching handy taskman i can see all the task, message (or address book) too;
only from handy taskman options -> close the task is terminated.

why this strange behaviour??

thank to all!