If you are looking for a medical reason I would recommend you go Google "AN UPDATE TO THE CRISLER HCG PROTOCOL By John Crisler, DO"
HCG on cycle is used to prevent testicular atrophy this will allow "the boys" to return to production faster. If you stick to short cycles most would never need to use it on cycle but long cycles as in longer then 10 weeks<<"this number is a random guess "you might want to reconsider the use of HCG cycle as long term atrophy can be a real issue for some but... HCG has also been shown to work in people who have been on cycle for years...
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2360778/
Fertility is another reason to consider hcg use, you may not want kids now but may in the future.
http://www.ncbi.nlm.nih.gov/pubmed/15514086
Two things to consider, recovering post cycle using hcg still has your natural production of luteinizing hormone suppressed. So this must be taken into consideration before you think you have had a successful pct. There is also health benefits to consider when on a long cycle so you should look into those before avoiding it.
I would have posted a few more studies to help elaborate but my internet is being a huge pain in the ass right now and Charter wont be here until sometime between 9am and 5pm Wednesday...wtf.