Bookworm
You are quite right there is nothing to stop you flying without a RIS or RAS outside of controlled airspace, hopefully everyone is sticking to the correct altitudes however you must admit that there is a risk of collision with some other IFR aircraft who is sharing the same cloud as you are and not talking to anyone else
I can only advise what I would do, as I am not prepared to take risks like that when I don't need to, that's where I choose to draw my own personal line. You can ask for a service (FIS) outside CAS but it is subject to radar cover and workload. I can only advise that you eliminate as much risk as you can and then check to see how important the flight is.
Hope this helps