Why development system is considered as domain controller ???

Hi ,

SAP recommends Production system as domain controller .Resaon is PRD is secured and has more availability.

But ,Most of the customer systems development system is set as Domail controller.

My guess on this point is , Development system will get installed fisrt in landscape and while configuring the STMS we have to use this system as domain controller.Later this scenario is not changed.

Please let me know why development system is set as domain controller. I have see most of the customer systems are having DEV as domain controller. That's why I would like to know about this point.

Thanks in advance.

Venkat