Motorway planning in these islands is often 'entertaining' for the motorist. I live next to the M6, which is currently being turned into a "Smart Motorway"* - going from three lanes to four, by having people drive on the hard shoulder. Cars do break down a lot less these days, but it's a most unpleasant and dangerous experience when they do in those circumstances. If there is a big incident, the entire motorway is blocked, with no 'free lane' for emergency use.
And there was the spur for the M54, which was only used by bin lorries going to the tip for the first ten years.
And anybody who used the M5 in the '70s and '80s, when they spent a decade turning it from two lanes into three, may, like me, still have the habit of using the 'old road' as a preference.
And the continuous widening of the M25.
And using the M2 as a lorry park.
Etc...
* The official terminology, not what I would call it.