Typically, for many travel insurances, there are very specific circumstances you need to meet in order to get reimbursed. You should read the policy very carefully to make sure it has the coverage you desire. For example, with illness, you usually can't just say "I'm sick" and get reimbursed...you'll need documentation from a doctor saying you were ill and that he advised you not to fly. Where-as, for a non-restricted fare, you can cancel for any reason. Also, keep in mind with travel insurance you will not be reimbursed for the actual premium you paid for the policy.

I find travel insurance to typically be a waste of money. There are certain circumstances when it is beneficial (Taking a dream trip vacation, going somewhere where natural disasters are common in a season, etc.), but for the most part I think people who buy travel insurance for every trip end up spending more in insurance than they would in cancellation fees (hence, why these insurance companies make money).