There was a thread on this...

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Anyway, I don't think there is any need, and it really compromises the appearance of glyphs, especially the Euro symbol.
The reason is that figure positioning in columns is now done by tabbing, rather than filling space with quads.

Having said that, I do try and make the Dollar and Sterling tab figure width.

Actually, it's a good idea if you're thinking about tab figure width, to consider designing all figures in a family to the same width from the outset -- lining and oldstyle, different weights, roman and italic.

Thanks Nick, and sorry about the redundant thread. I now see the original one here (asked in an eerily similar way!).