I do not know if anyone still believe heaven is a reward . Some people could still be working hard to earn heaven but the Bible after thorough studyshows that it is God's gift to man through Jesus Christ.
This is probably hard for most to grasp. But if it is a reward then we have to follow every commands of God but the Bible says that if we offend in one we violate all ( James 2:10).
But then if it is a gift then some people will think it is too easy. It is not easy because it took Jesus, God's Son to come to earth in human form and be the sacrifice for our sins.
Then some may think if it is a gift then we do not have to do anything to receive it. I believe we obey God as our thanks for His gift of salvation.