Why do people rarely execute options and instead sell the contract?
Is it because the options allow you to control a lot more shares
than maybe you have capital to purchase?

What if the contract expires in the money, and you haven't sold the
contract, does it automatically execute the option to call or sell?

Is it hard to find good opportunities when looking for options? The
stocks I follow, it seemed the options listed were unrealistic, or,
after factoring in the premium were hard to make substantial gains.