Why /usr/ports/UPDATING and /usr/src/UPDATING files are needed?

[Yuri]

When I am in FreeBSD I have to be always aware that I have to check 
these files before upgrading the system. And I need to do some custom 
things myself.
When I am in Ubuntu apt-get just does everything by itself without 
manual intervention.

Why FreeBSD doesn't automate things that are in UPDATING files as well?
In almost 100% of cases it's no-brainer. Why can't portupgrade just 
execute a script instead of posting such script in UPDATING file and 
have me run it?

Yuri