I applied for a job as a postman last year and was really shocked to find out that hundreds of people had applied. I was shortlisted and had to attend a series of aptitude tests along with 50 other people.
I was fortunate to be offered the one job they had but I am sad to say that I absolutely hated it and left shortly after.
I'm sure that not all of the post offices work the same way, but this one was atrocious with no regard for the condition of peoples mail and so much skiving off done that I was flabergasted.
It's no surprise to me now when I find mail that has gone missing in the post and that mail deliveries can take ages.
I'm going off the point really, but I was just trying to say that yes, they do seem really hard to come by. Keep persevering and I am sure you'll get hired and be a lot more conscientious then the people I worked with.