Logrotate doesn't run hourly in Ubuntu 13.04

I am currently experiencing some issues with logrotate, and running them hourly. After some investigation I found the following:

/etc/crontab:
# m h dom mon dow user command
17 * * * * root cd / && run-parts --report /etc/cron.hourly
25 6 * * * root test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.daily )
47 6 * * 7 root test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.weekly )
52 6 1 * * root test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.monthly )

ls /etc/cron.daily/
logrotate

ls /etc/cron.hourly/
# empty

I think that means the following logrotate will not work:

ls /etc/logrotate.d/nginx
/var/log/nginx/*.log {
  hourly
  # (...)
}

Is there a reason why logrotate is not set to run hourly in Ubuntu?