Sweet apple acres is actually a mass scam, and granny smith secretly invested tons of money into independant-growing trees that self-seed and care for themselves. It explains why the only work Applejack ever does is kick them.
Grannysmith then erased all memories of the investment from the other ponies minds, her first subject being Macintosh. Unfortunately Macintosh's memory was erased too far, which explains his lack of english vocabulary.