I'll wait for more replies before I totally write off the concept, but your experience matches mine entirely (esp. the bit about more easily accommodating it in a jacket pocket). Besides, and I may be totally weird on this, I don't think passports look all that bad uncovered - the crests are interesting enough. Mind you, I do slightly miss the old-fashioned black leather (or leather-substitute, who knows) British passports. (first person who now goes on to suggest that if I miss them so much, I should get one of those mock-old-British-passport leather passport covers, gets an ironic clip round the ears.
Here we have another category of lack of understanding for passport cases, this being is aesthetic and protected by guardian angels. He belongs to a nation which has no enemies and do he has no need to conceal his nationality from various other kinds of beings, some of which are attracted to railroad stations or other places of special interest. He is also quite healthy - no trace of paranoia. He may be able to defend himself in any situation.