You don't want to padlock the cable to the car and the charging post. What happens when someone drives off forgetting about it? We've seen the pics from petrol stations.
And there is no chance I'll be able to get parked near one. I park in the street as I have a flat. Its difficult enough finding a spot big enough for a car when some idiots like parking one car in the middle of two spaces because they cant park properly. When there is a space, you have to watch for trees, lamp posts and wheely bins blocking your door before you park before they put on some charging posts.
Stick these things in and you'd either need to space them along every street in the UK at half car lengths or you'd risk not being able to park at one.
If I'm driving across the UK and run low on juice, I fill up in minutes with petrol. I'd have to plan a route in advance with a hotel at the right distance down which has charging posts in its carpark.
Plugging in cars to charge them is an impractical idea.