Question: Would you be kind enough to explain the nuance between "pitiful" and "pitiable"? My Oxford Advanced Learner's Dictionary shows two similar meanings for the aforementioned words.

1. deserving pity or causing you to feel pity.
2. not deserving respect

I am confused as to why there are two different adjectives with almost the similar meaning and examples.

Answer: 
I'd say that pitiful might be either of those two definitions (you use context to know which is being used), but pitiable is only the first.

A coach might tell his team "Your guys on defense were pitiful today". He's telling them that they did a bad job. But you would never use pitiable there.
I would distinguish them as 

**Pitiable** is something evocative of pity or sympathy, but not necessarily in a bad condition

**Pitiful** is something deserving of pity, and disadvantaged in some way

Consider a cute kitten giving an imploring look in a picture - she is **pitiable** and you mentally go 'aww, what a cute & weak creature, let me fuss over it!' even though its perfectly fine and not *pitiful*.

Now consider a thief or molestor who got beaten to a pulp by a crowd. He's in a **pitiful** condition with multiple fractures, but your initial response might be vindication rather than sympathy; he's not *pitiable*.