I suppose the issue could be that having it auto apply might leave you in a position where you'd get so used to it that you could possibly park up, it failed to apply and you walk away.. It's not fail-safe in that respect.
I must admit to having been nervous about the electronic brake anyway, as my first experience of it was on a Toyota Avensis. Not only is that one in a stupid place (under the dash) but it works opposite way round, i.e. you push it to apply. Totally counterintuitive. Plus, according to the manual, it wasn't guaranteed to work below -7° C...
Alan