They might have tested it and found that it just wasn't an advantage to having more RAM.
The RAM they have in there is pretty fast and the SSD to RAM might be fast enough and Android's RAM management good enough that more than 2GB just isn't necessary (but I haven't seen those tests, just guessing).
There could also be a battery life reason.
It looks like the test/dev/beta version of the Shield did have 4GB of RAM, so I'm guessing there was a decent reason they reduced it.
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They might have tested it and found that it just wasn't an advantage to having more RAM.
The RAM they have in there is pretty fast and the SSD to RAM might be fast enough and Android's RAM management good enough that more than 2GB just isn't necessary (but I haven't seen those tests, just guessing).
There could also be a battery life reason.
It looks like the test/dev/beta version of the Shield did have 4GB of RAM, so I'm guessing there was a decent reason they reduced it.
http://www.droid-life.com/2014/04/23/nvidia-shield-2-gets-be...