Reference models are NOT made available to the general public, what are you on about??? At CES this year Nvidia were showing off a tablet which was a reference model just for showing off some new tech. It's not in mass production and is not sold to the public.
It is you who does not know what a reference model is. The Nexus 4 is NOT a reference model. It IS a consumer phone available sim free and on contract from networks. Why is this such a difficult concept for you to grasp?
I think the point you are struggling with is that these days developers ARE the general public. Not all apps on the Play store (or the Apple store) are major firms with access to formal reference models. The NEXUS line started
as a vanilla android phone with less lock down than a standard android phone aimed at developers who wanted such things. In the early days of Android vanilla wasnt very pretty so it was not a very popular consumer model. Consumers wanted Sense and Touchwiz to pretty things up. Devs liked it as it didnt have bloatware to contend with.
More recent Nexus models have become more mainstream. Android is prettier. Updates have become more popular and the consumers are more aware of latest versions etc. The Nexus line is now a consumer model but is still favoured by many developers as it has the most up to date software.
It really isnt rocket science and doesnt need pages and pages of arguments ......
Do you really think that Google keep a phone unlocked because thats what consumers want ???