Bump! I'll have to say that this is the most touchy subject in any steroid forum which often results in name calling and insults. Here's some links that sum it up nicely:
https://thinksteroids.com/articles/testosterone-base-steroid-cycle/ - This is very fair and short article on the matter.
http://www.steroidal.com/testosterone/testosterone-in-every-cycle/ - A very insightful article explaining why this is a long-held belief.
IMO, the reason "why" test must be the base is the feeling that it provides. Test truly makes one feel quite good about themselves and possibly even euphoric for many people. It really provides that "godly alpha male" feeling that no other steroid can match while being the most universal in its' abilities. Those who have not tried it will "understand" once they do. Orals obviously suppress ones natty test levels so that libido will definitely be affected with long-term usage. Test will counter these effects from orals. Simply put, Test is the most effective steroid ever invented and can be stacked with anything.
On the other hand, Test is also a "wet" compound as opposed to a "dry" compound. It will aromatize (which can be combatted through the proper ancillaries), be 5a-reduced to DHT (can be bad for some people, but can also be combatted through the proper ancillaries) & increase weight (which is bad for people wanting to maintain or drop to a certain weight). These qualities make it bad for certain individuals with differing goals. I will argue that oral only cycles can also be effective, though less so than test base cycles. One can theoretically keep natty test levels higher with SERMS and AI and use orals to get good results. Also, this will obviously meet with disagreement from "traditionalists", but there is also the idea of "pulse cycling" orals to avoid suppression at the cost of some results. "Traditionalists" will definitely doubt the effectiveness of this method, but they have definitely not tried it and are not keeping an open mind. Please see below article for explanation:
http://anabolicminds.com/forum/steroids/62121-how-pulse-orals.html - "Pulsing Method" for oral steroids