A couple of points to add:
For many folks it is the comprehensive version of vehicle insurance that they want - this goes way beyond the basic cover and so an extra premium can be charged.
In the case of the "basic" EU cover, I think this becomes a murky subject because there exists (in the UK) RTA cover = Road Traffic Act cover.
The insurers don't publicise this fact, and they certainly don't try to make a hard sell of it, so the usual product on offer "below" fully comp is cover for TPF&T (Third party, fire and theft) - this goes beyond RTA cover and so, again, an extra premium is requested.
In my case, last time around, I paid an additional £19 for 365 days of EU cover.
(You can have some great conversations with your ins broker when renewal time comes around!)