So do I!
Next time I drive down the M1, I'll have a look to see how far down you need to be to get the distance to London shown on a sign. London is shown on directional signage almost from Leeds city centre, and for directional purposes it is shown again on approach to the M62. But I don't think any distance is indicated on any signage until south of the M6/A14. There is this oddity just before the M62, but no distance is shown.
Once south of the M62, there does not appear to be any distance signage at all until this sign, which is south of Wakefield; and even then, travellers to large/largish places like London, Luton, Milton Keynes, Northampton, Leicester, Nottingham or Derby have no idea how much further their journey will last!
Perhaps their rationale is that everybody will be using satnav?