This world is temporary. We all die sooner or later, and the game is up, and you go on to your eternal reward (hopefully). If you don’t do Mitzvos, then what was the point of your life? What do you have to take with you to Olam Haemes (the True and eternal world)?
The purpose of this world is to merit reward in the Eternal World-to-come. If you don’t do Mitzvos, you have missed the point and your life and death are meaningless.
Also, as Mobico said, it is incredibly fulfilling and brings meaning to your life and to everything you do. Being Frum, learning Torah and doing Mitzvos, and living a life dedicated to serving Hashem is the most amazing and awesome thing in the world!
Everyone values and needs relationships. That is probably the main thing that any human needs and wants. A relationship with Hashem is the best and most fulfilling relationship a person could ask for. (which is also the reason that I don’t consider being single to be a crisis.)