I have to give credit to Sony for trying to redefine the "high-end"/DSLR camera market. "high end" meaning everything above P&S and Bridge.
The traditional DSLR market segments from "bottom to top" are roughly as follows;
"Soccer Mom"/newbie
Hobbyist
Enthusiast
Professional
Which is why DSLR's are designed to give the user controls for varying photographic needs.
Conversly, with the A7 cameras, Sony is attempting to define the market by the type of photographer you are vs. how "serious" you are. The A7 is best suited for the Street Photographer or even Sports. The A7r is for the landscape photographer or portrait/fashion ( a cheaper, lighter, medium format type option) while the A7s is for the low light shooter and/or for video. Can each camera perform well in the other areas? Certainly - but if you define yourself as a specific "type" of photographer vs. "beginner - amateur - pro" than Sony has a camera for you. The area that is somewhat lacking is probably Sports due to the inherent advantages of a OVF and mirror - although that gap may be closed soon.
The following article splits it out even more;
http://www.bhphotovideo.com/explora...iew/sony-a7-series-which-model-suits-you-best
The traditional DSLR can do almost everything very well because they are designed to appeal to every photographer within the traditional segments.- while the A7 cameras can do most things very well, a few things not so well and a few things excellent.
I don't know if Sony will ultimately be successful with this strategy, but the continual focus on Emount seems to say that so far it is working.
The A7 is absolutely not a sports camera -- Putting aside the EVF issues, it has a pretty slow frame rate, mediocre autofocus. Combined with the lack of long lenses in the FE mount, it would be pretty laughable as a sports camera.
But it is intended as a "general purpose" shooter. It can handle sports/street/candids better than the A7r, and most people don't want/need 36mp for regular use. The A7s is the specialized low light shooter, but many people want more than 12mp.. So the A7 is a bit of a sweet spot in terms of price/resolution/performance.
Sony isn't alone in providing cameras based on "type" of photography. The traditional dSLR companies already do the same thing.
Canon: Sports and wildlife shooters: 1DX and 7Dii. Studio camera -- 5diii and 6d. Street/candids/wedding camera -- 5diii. Video -- 5diii and 70D.
Nikon -- Sports, the older D300 which may eventually get an upgrade, and the D4s. Studio/landscape/products -- The D810e. Low light specialty -- the DF. All-arounder APS-C, the D7100. Candids/street/wedding/general purpose full frame -- the D750 or D610.
So Sony is finally arriving to the game -- of high level photographers want/need more specialized niche fitting camera. They previously did more of a 1-size fits all, with the A99 being their sole full frame offering.