Are NSI and SSAIB Installers being fair to Domestic clients?

Why do NSI and SSAIB approved Installers believe that they have the right to put their own engineer code in to a new domestic installation?  When, the client has just paid good money for the system, surely the system is the clients at that stage and not the installers.  Yes, the installer will say its down to security but in reality they are looking to tie the customer in to them and no one else.

Yes, the installer will, upon request call along and change the code back to that, what the control panel was when it left the factory. But they will charge the standard call out rate which could be well over £100.00. If the client has taken out a maintenance agreement why is this service not included? If the client does not believe they are receiving good service or have realised they cannot afford the annual maintenance agreement figure then surely, having paid good money for their system they should be able to go elsewhere without being penalised? 

By domestic client we are not talking about High Net Worth Individuals but ordinary people, single parents, the elderly and in some cases the vulnerable.

The security alarm industry does not seem to want to get involved in this. The governing bodies are focussed on improving membership figures and income streams. There does not seem to be anyone who is willing to fight the corner of the domestic alarm users.  Perhaps AlarmCare UK will?