How can breakups rip the heart out of you but can still leave you begging for your ex-lover's affection years after the split?

Because there will always be a part of them that sticks with you. You will always remember them as they were before they hurt you and your mind plays tricks on your emotions and you tend to think that they're that person even if they're not.

Because that person hurt you when you broke up but you don’t have to stop caring or loving someone if they leave. It’s ususlly not what happens. You will remember the good times over the bad because you will miss them.

Breakups are always hard, it can be difficult to re-adjust to being alone and reconnecting with the person you were before entering the relationship. There can be feelings/cravings for "the good times" which can hurt especially if you know that you can never get them back. If you're just craving the more physical aspects of a relationship like back hugs, holding hands, etc. those cravings could be satiated but when it comes to different types of affection like being complimented or being listened to; that may be a signifier to get back in touch with yourself. Give yourself compliments, have some time alone to re-evaluate why you feel like you still need affection from someone who can no longer maintain that level of affection for you. You are not crazy for wanting affection from someone you used to love, but you do have to readjust.