Why cant they? Maybe they cant if the shareholders have stock in Yahoo as well But there is no other reason why they couldnt if they wanted to.
lots of free directory avaible you can try them instead of paid options.consult with me I will help you.
yahoo directory is a paid one .. ..but Google referred yahoo in the webmasters guidelines When your site is ready: ........................ ................................. * Submit your site to relevant directories such as the Open Directory Project and Yahoo!, as well as to other industry-specific expert sites. http://www.google.com/support/webmasters/bin/answer.py?answer=35769