All of your remaining friends and family will believe this, and the case will be so bad that your name will become associated around the world for the sheer heinousness and reprehensibility of the things you supposedly did. However the djinn is willing to bind himself to not doing this, but you have to pay him $1 right now.
If "nothing matters after you are gone", then you wouldn't even be willing to pay $1 to avoid this scenario.
You care about the wellbeing of your friends and family after your death, even though you're not "around to observe it". So there are at least some things that you value in life, that you still value after death.
Many people being value being respected in life. There's nothing particularly different about extending that value to being respected after death. At least not if you already assign valence to other values post-death.
Few people really don't care what happens after they're gone. We almost always want something to linger on, be it descendants, a master works, or just the world.