Quite simply, because there are no natural (negative) rights to healthcare, food, or education. All these things are positive rights (i.e. a right that does not exist until it is created by a contract). Negative rights (such as the right to life) cover things that are natural to all people, such as the right to life, free speech, expression, etc.
Or to use Wikipedia's comparison: "positive rights permit or oblige action, whereas negative rights permit or oblige inaction".
Or to use Wikipedia's comparison: "positive rights permit or oblige action, whereas negative rights permit or oblige inaction".