Why do you have to practice a skill everyday? You sometimes have the strengthen a skill that you already have mastered. This feature just cost a lot of time and you'll basically have no time left to do a new skill.
Like elizadeux said, you don't have to do it, but most of us know that feeling of wanting to keep the tree golden. See this neat blog post from a fellow Duolingo user on how to keep your tree golden: http://gregreflects.blogspot.com/2014/12/how-to-make-gold-duolingo-tree.html