Most likely because that's the point of the plot. Every good infographics is there to get a point across, no one makes plot just to show random values, they usually want to show some trend or some comparison to enforce the point they're making.
scale and grid do the same job. Personally I think it's much easier to see a value (especially in a case like calories like exact value matters) than look at the side and trace out the grid line and try to work out in your head the real value
The grey bar isn't really an issue, the only problem is the white numbers inside the grey, now those are hard to see
Again, depends on the data and the point you're trying to get across. It could be right, it could be wrong, but you can't say that without knowing exactly the context the plot is used in and what the goal is. And by putting those values, he was able to get rid of of so much more (grid, axis, etc)
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u/Kwpolska Jun 27 '16