While there has been a lot of noise of late respecting the importance of profiles, this in many ways puts the cart before the horse. I will agree that simplicity and a low entry barrier are important for widespread adoption. At the same time, however, one might be more focused on real user need rather than the need of existing vendor product implementations.
If we take a more market-oriented perspective – we would then focus first on application schemas – these after all define the needs – the vocabulary of the application domain in question. Here we see a wide variety of demand. Some areas really need unusual geometries like Clothoids or Geodesics – unusual only to traditional GIS, while others need very simply structures (e.g. web news feeds like geoRSS). To expect a single profile will cover all of these is quite unrealistic. This is the beauty of GML – it is rich enough to cover this wide range of application domains. At the same time, we only need pick and chose what the particular application domain requires. If no Clothoids then don't use them.
In this manner we see that Application Schemas drive profiles – and a user in a given application really focuses on the Application Schema and the profile (subset of GML components) that this application schema requires.
This is not a critique of GML Simple Features (GML SF) – but simply to point out the value of a more application driven perspective.