Remove one leg and the tripod topples. The tripod is not some ipod with a lot of the songs stored in it where you can lose one and still play many. All the 3 legs are equally important and even one leg getting damaged can bring it down. You can always say that a chicken doesn't fall down with only 2 legs nor does a human, but a chicken is what it is - a chicken, and a human could have done more things if he could have used his tail as his 3rd support.  Imagine the convenience of sitting on the tail - you are neither standing nor sitting. You can do things at ease, like answering the calls of nature with amazing comfort!