It isn't about him not caring. He's just taking you at your word that you need to cancel. From what you said, you didn't tell him why you were cancelling. Even if you did, it isn't unusual for clients to cancel, and most T's won't call to check up on the reason unless it has been pretty explicitly stated that they want a return call/contact.

The only time my T ever called when I cancelled was because we had talked on the phone the night before because I was suicidal and had a plan. When I cancelled the next day because I was physically ill due to an attempt, he called to find out what was going on because he suspected I had made an attempt. Otherwise, if I cancel, he simply respects my decision to do so and if it needs to be discussed, we talk about it the next session.