The reason this is happening is that the default uv attributes are Vertex Attributes, not Point Attributes.
The SOP to DAT will only show the uv attributes out of the box when you set its Extract parameter to Vertices. You’ll notice that if you set Extract back to Points, not uv attributes are available.
Likewise, the reason you see them after adding a Point SOP is that you are then adding uv Point Attributes.
The SOP to CHOP only operates with Point Attributes.