Although I agree that the $100 upgrade to 8GB is a no brainer, there are two issues. The first is availability. I do not think any Apple Stores carry 8GB MBA systems as standard stock. The second is price. If someone is price conscious or on a budget, that extra $100 may put them out of the range s a system.
Even looking at the refurbished prices, there may he hesitation on the term "refurb" and it being buggy. I personally, would entertain a refurb model if there was one that met my requirements, but someone like my wife would never go that route.
Speaking of my wife... My wife is only running a 13" MBA with 4GB of RAM (Mid 2012 - 1.3/4/256). I would not say that she is a power user in the sense where she is a programmer, phot editor, or video editor but she uses Word, Excel, Preview, and Safari all at the same time.
You may say, "so what." The thing is that she usually has about 20 word documents, 6-10 excel spreadsheets, a handful of PDFs, and probably 15 safari tabs open at any given time. She sometimes throws Quicktime in there when she is reviewing a video recorded session of one of her clients (she is a Speech Therapist).
Knock on wood, but she has had no major issue with the laptop. I would say, if anything, Word freezes up on her and we need to do a 'Force Quit' on it. But it has been so infrequently, that she has not complained. Granted, I brought her over from a Windows environment where she ran a beefier setup and constantly had system crashes utilizing a similar work process scenario.
I think the Mac environment on a 4GB system, currently, runs great for probably 90% of the general public who would be getting into a Mac system.
Oh, and she easily gets a full day to day and a half of battery life.
