why do not put user's objects into the SYSTEM tablespace

 why do not put user's objects into the SYSTEM table space:


EXAMPLE:
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SQL> connect sat/sat
Connected.
SQL>
SQL> sho recyclebin
SQL>
SQL>
SQL> create table foo(a number) tablespace system;

Table created.

SQL> drop table foo;

Table dropped.

SQL> sho recyclebin
SQL> create table foo(a number) tablespace USERS;

Table created.

SQL> drop table foo;

Table dropped.

SQL> sho recyclebin
ORIGINAL NAME    RECYCLEBIN NAME                OBJECT TYPE  DROP TIME
---------------- ------------------------------ ------------ -------------------
FOO              BIN$HW/MeRuIHc3gVAAhKLXStA==$0 TABLE        2015-08-16:14:49:57

SQL>

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