I would say most emphatically NO. I want my core to cover general rules including non-combat travel and exploration. I want my core rules to be a tool kit that extends beyond the encounter and beyond combat. Setting books should cover specific concerns about their settings, sure. Perhaps with more sophisticated detail when it's important like the desert setting rules of Al-Qadim.
But what if I want to build my own setting? Shouldn't the core offer me some support? And shouldn't that support be shared as part of the core rules so that the general rules for my campaign world are similar to my friend Brian's, or Rob's, or Stephen's, particularly if we are all trying to play the same basic game?
No, general rules for all sorts of things I may want in the core. Specific overrides, extensions, or gloss-overs can be put in the settings.
There are two view-points here, prefab and diy. Also, I may be a bit biased because I tend to travel around the world a lot and enjoy the challange of overcoming the cultural barrier.
From the prefab (or specific) pov, having all the rules to emulate a specific culture in one place beats generic rules by several magnitudes, like with Al´Qadim.
From a diy pov, having a group of generic rules to adopt to a culture may be neat, but you need to know the culture you want to create or emulate, else it´s an intellectual waste of time.
To draw a real world analogy, for me as a german it´s as difficult to be in Mumbai, India as it is to visit New York, USA. My "generic" social rules I know by heart don´t mean



