זה א-לי ואנוהו א-להי אבי וארוממנהו
This is my G-d and I will glorify him, the G-d of my father and I will exalt him.
We have a problem. This has been a problem for the last few hundred years or so since the enlightenment. It was a "light" that brought not a small amount of darkness as well. It is large numbers of Jews going off the derech. We have a tradition going back 5,000 years to Avraham Avinu for which we have undergone untold suffering in order to preserve. It started with Avraham [i.e. the entire Jewish people!!!] being thrown into a burning furnace for his beliefs and that more or less tells a lot of the story since.
People feel "This is not for me. I don't want or need it". Ontologically, saying that "I am an atheist" means nothing. That just means that the person has for whatever reason decided not to believe but has nothing to do with objective reality. So people drop the whole thing and move on [or "down" according to my taste] in life b/c of their feelings - regardless of Truth, revelation, tradition and history.
There are many reasons to remain observant. One is that if one doesn't, he is rebelling against G-d who gave him life and everything else. [Of course the non-believer often doesn't accept this premise]. Another is that one's parents lived a certain way. His grandparents lived the same way, all the way back for thousands of years. And this person decides to break that incredible chain. In the absence of very compelling reasons to change [and cause incredible pain to his family and friends] - it is really the moral thing to do to keep with the system. Both on a familial level and on a national level. When a person is born "on the team" [i.e. his family and Klal Yisrael as a whole] - that obligates. To reject tradition is to be a to an entire nation [no less!!!]. The problem is that moral arguments prove facile when presented to one with no obligatory sense of morality. Rejecting Hashem and His Torah proclaims that the one and final arbiter of morality [or even the question of whether there is such a thing] is the person - with all of his biases, desires and egotism. One must also appreciate that when a singular individual makes a decision to abandon Torah, that will affect his children, grandchildren etc. etc. whose trajectory will be secularism and all that entails. To give a contemporary example: Benji from Netanya is descended on one side from the Vilna Gaon, on the other from Rashi. The reason he is not frum is b/c his father decided to become an apikorus despite his father having been a rabbi with an IMPRESSIVE friend. [Fortunately - Benji's one and only daughter is frummer than frum!!].
So sadly, these arguments usually [never?] won't work to convince a person to remain within the faith community. Such a person rarely if ever has a national consciousness or will refrain from doing what he feels like b/c of a family tradition.
But that doesn't make it less true.
זה א-לי ואנוהו א-להי אבי וארוממנהו - Hashem is not only my G-d but part of a loooong tradition. My father, his father, dating all the way back thousands of years.