Why is learning auxlangs a hobby?

A language is much more than beads of words tied together by the string of grammar. Earlier I used to think, I could learn any language if only I could get my hands on its grammar and a dictionary. I was naive. Because that's not how things work when it comes to languages. 

A language is like a jungle. A grammar, like a map, can give you a rough idea of what to expect when you are going inside. By the same analogy you can think of the dictionary of a language as a catalogue of all the plant and animal species in the jungle. Both are useful but never sufficient because there will always be surprises. You may suddenly come across a dilapidated track that's nowhere on the map. Or you may find new species that are yet to be catalogued. There is vegetation that you can smell, touch and taste but your grammar book doesn't explain how it came to be. And if you have come into the jungle of your own will, you think of all this as an exciting adventure.

An auxlang is also like a jungle, albeit a small one. Another difference lies in the fact that each tree is planted by hand and the tracks are carefully designed for a purpose. You won't find them leading to nowhere. This careful plantation takes out the surprise element. And because the whole forest is often the work of one man (or a team in some cases), these little forests are more like a garden when you compare them in size. Perhaps that's why learning auxlangs is 'a hobby', after all going to the Amazon isn't the same thing as going to the Baradari Gardens here in Patiala.