CREATE VARIABLE used in a compound-statement

Any reason anyone can think of, or documentation explaining why, a CREATE VARIABLE statement is not a valid procedure-statement?
[http://www.ibm.com/support/knowledgecenter/ssw_ibm_i_73/db2/rbafzsqlprocstmt.htm?lang=en]

A routine [or dynamic] compound-statement can have a SQL-variable-declaration [DECLARE SQL-variable-name], so a variable can be had, scoped there. But why can I not effect the creation of a global variable name? I am unsure, but seems DB2 LUW 11 may allow the CREATE VARIABLE outside of a SQL-routine-body [thus in none of: procedure, function, or trigger], so apparently that leaves a dynamic compound-statement as the only procedure-statement usage.? For me, IBM i 7.1 DB2 SQL would not allow the CREATE VARIABLE in a dynamic compound-statement.

Seems a stupid restriction, given I can circumvent easily enough, by issuing the request dynamically; e.g. in an EXECUTE IMMEDIATE. But why should I have to?

And that circumvention had me encountering something interesting; seems in 7.2 [I was looking at newer docs than the release I was on] the /string-expression/ of 7.1 has become just /expression/ on 7.2, and apparently "execute immediate expression" will finally accept a literal\constant string-expression rather than only a variable; a capability that apparently had always been limited to PL/1. I can not verify, so if anyone wants to humor the group...