Unreliable?
That is the whole philosophy of the RAT. I'm not saying to scrap pitots, but to have a backup which is not prone to icing, spiders, wasps etc. By your logic you would scrap the RAT because it's complex and prone to failure? The RAT is also a last resort, and not designed to take the place of the aircraft systems.
I don't really get where the RAT comes into this? They are deployed to do the task of either a hydraulic pump or electrical generator both of which are complex machines with many moving parts.
There are normally 3 pitot probes with the 3rd being the standby.
A pitot probe has no moving parts and is inherently more reliable than something which would have many moving parts. That's why I don't agree with your idea.
If you're proposing a 4th RAT type system then I'd have to ask - where do you stop. If you have backups for every backup then quickly your aircraft becomes too heavy to leave the ground.