DB2 developers can't create table in own schema but SQL and Oracle devs can. Justified?
They probably do this because storage allocation on the mainframe is much more complex than for unix or windows platforms.

zOS is basically a very modern sophisticated piece of harware and operating system that is emulating a 1960s mainframe. In much the same ways as the latest Intel chips are emulating a 1980s 386 chip.

The problem is that the very low level close to the wire disk I/O which was necessary to get high bandwidth and and quick access times on the original hardware is "baked in" to the OS and many applications. So all disk storage for legacy apps deals with channels and volumes. A volume is a "pretend" 3330 disk with 8GB or 32GB of storage usually allocated as a piece of a real nTerabyte raid system.

To define tables properly in zOS DB2 you need to create tables spaces which in turn requires you to allocate storage on specific volumes this is fairly messy as four or five entities need to be linked together TABLE -> TABLESPACE -> Volume Group -> Disk Volumes + Index -> IndexTablespace -> Volume Group -> Disk Volumes.

Basically your DBAs are saving you a lot of grief by not letting you play with the matches.

P.S. If you use the modern half of zOS (Unix Systems Services) this all becomes irrelevant but it's going to be a long slow migration!