I think computers with 3GB and 6GB of RAM are less popular because buyers don't save money by buying a computer which has slightly less RAM. They also maybe paying slightly more money compared to a laptop with 2GB or 4GB of RAM.
The faster performance may not be very noticeable on computers which has an extra 1-2GB of RAM.
The faster performance may not be very noticeable on computers which has an extra 1-2GB of RAM.