You are confusing on board real time monitoring vs 'prediction'. The on board RAIM works only in real time and gives you the current status of the accuracy and GPS functionality. The RAIM 'prediction' for a geographic location works out the expected satellite positions at any given time and works out when and if there could be a lack of satellites to satisfy navigation requirements.
Airbus now only requires that pilots check RAIM predictions when the destination has terrain around that may mask satellite reception or when flying an RNP-AR approach with legs that have RNP of below 0.3NM. This is because GPS coverage is now considered available 24 hours a day down to 0.3NM world-wide except if there is terrain around that masks signals.
Again, your receiver can check current satellite status but it isn't going to know whether in 4 hours when you get to Kathmandu and you need to do an RNP-AR approach due weather, if you'll have the required satellite coverage. You want to know that before you get there, not once you get there.