Voy a trabajar
On Rosetta Stone the sentence Voy a trabajar is given, why use the "a". It seems like this would translate I go to to work. It seems to me the "a" is not necessary.
Ir + a + infinitive = going to do something
Voy a caminar = I'm going to walk
Vas a hablar = you are going to speak
Va a dormir = She is going to sleep
Although you do not "hear" the "a" in English, "ir a [infinitive]" is just a pattern in Spanish that means "going to do something".
There are many patterns that are different in a language "just because".
I suppose this would be similar to the "personal 'a' ", in that it does not really have an English equivalent. It just is.