Originally Posted by
RickR
Perhaps they fear you won't be able to leave, i.e., being barred from every other country? But, it seems your home country is likely to let you back in.
That's the reason behind at least some of these policies.
There are a number of countries that agree to extend the validity of the passports for six months beyond expiration for the purposes of readmission. These are members of the so-called 'six-month club'.
http://foia.state.gov/masterdocs/09fam/0941104X1.pdf
The US, for example, will admit otherwise admissible nationals of six-month club countries for a stay up until the expiration of their passport. Otherwise, they will not admit nationals within six months of the passport expiration.
Some info:
http://www.state.gov/documents/organization/87474.pdf