I don't know; my wife is limited to primarily these things[1], and she was always asking me why her computer was so slow; she refused to close most of the open apps or browser tabs for various reasons.

I bought here an air with 16GB of RAM and all of the complaints have gone away.

1: Though s/Facebook/Pinterest/, and occasionally a non-word office app open.

Which is an ipad use case, I think people aren't so offended by the air, which could be viewed as "ipad with keyboard" but by the macbook pro with 8G, because presumably a person using it for "pro" work would be doing some heavy lifting to justify the "pro" bit.

But, I think pretty much everyone understands apple tends to have a social signaling aspect tied to it, too. This is why you see plenty of PowerPoint warriors/middle mgmt toting them around too, because "pro" even though their use case for the machine is frequently little more than light office work (ppt/word/excel). So, why not offer it with 8G, they get their social signalling for cheap, and everyone else gets to pay $$$$ for the real configuration.

Someone who only cares about Word, YouTube and browsing Facebook also doesn't need a $1,600 laptop with an 8-core CPU and a chunky GPU, they could get by with something much less powerful and probably wouldn't even notice the difference - and if anything, having only 8 GB of RAM is more likely to cause performance problems than not having a fast CPU or GPU (the modern web and modern apps are pretty memory hungry especially if you open a lot of tabs).