I think it is the same mentality which causes people to park ridiculously close to you in e.g. a supermarket car park when you have taken the time to park in a totally deserted part of the park.
I think some drivers are so unsure of themselves and their abilities that they need to
'line' up their car with yours when parking or tailgate you , as above , on the roads - it saves them having to calculate the necessary responses themselves....
We have a
'titchy' little Smart car which we use a lot in and around the City.It is surprisingly nippy (Brabus tuned and a turbocharger on all off 700c.c.

) but other drivers still feel the need to sit on our rear bumper
James