The pic with the colours chairs works so well as they are the only coloured things in that set - if you want them to be as stunning - I think you need to emulate the set - ie white walls and white floor ! If you go with the darker wood floor that you are considering - personally - I think it may loose a little of its Wow ! ( will look fantastic with white plates !! And the three colours used as serving or side dishes /napkins etc )

You may want to look at Riva 1920 and Girsberger. We (Whetstone Oak) do also use American Black walnut.

At least 80cm to 1m wider and longer than table will allow chairs to be pulled out etc without rucking up carpet. Your local carpet shop should be able to cut you a remnant or off cut to size and have the edges whipped to form a rug.

In a lot of cases, I suspect the answer would be for the same reason you do eat at a table - it's what people generally grew up doing, it's what they're used to doing and, being part of the television generation, it's just too convenient to do otherwise. Ironically, I don't tend to watch very much television at all, except when I'm sat, tray in lap, eating ... Another possibility is that not everyone has the space for a permanent formal dining table, and use one with fold-down leaves, for example, which can be hidden away behind an armchair, or somesuch, and wheeled out requiring the moving of other furniture) for special occasions - entertaining, or xmas dinner. For my own part, it's a combination of familiarity, and the fact that it's simply more comfortable to sit in an armchair, or on a sofa, tray on lap, even if I don't bother putting the television on.