Even though most Americans claim to believe in God, more and more embrace the idea of being “spiritual” but not belonging to an organized religion or church.

I haven't watched the video yet.  However, looking at the question, I can make a simple observation.  Buying into a spirituality without buying into the religion from which the spirituality grew, risky.  Religion, in fact, is a collection of values and spirituality.  So, when people say they are spiritual and not religious, they are probably opposed to obedience and doctrines.  So, the only spirituality they will probably get attracted to is a spirituality that makes them "feel good".  These spiritualities are usually man-made.   I will post another response after watching the video.

I also haven't watched the video.  On the aspect of being "spiritual." some years ago, I worked with a woman who told me exactly that:  I am spiritual.  My response floored her.  I simply said, "so is the devil." 

As far as why a person doesn't buy into the "religion" aspect, there are many reasons; I'll only name a few. 

A.  Poor catechesis - this is a generational reason. There is little understanding of our faith and you don't know what you don't know so you don't know you have gaps.  You can't teach what you don't know. 

B.  Lack of understanding of Catholic traditions, starting with sacramentals, moving through vestments, religious orders, (why do the women wear odd headgear and long dresses?) and so on. 

C.  Disillusionment with the hierarchy, starting with the Vatican.  McCarrick only got his hand slapped.  James Altman, who has been speaking God's Truth, has been basically cancelled.  James Martin gets a public pat on the back by the pope. 

D.  The constant asking for money, especially when so many are unemployed.  Not everyone is unemployed by choice as the media would have one believe.  There is a perception that the Catholic Church has piles of money, yet they cry poor.

E.  The expectation of "what's in it for me?" instead of "what can I give to God?" or "how can I be His Hands and Feet on earth?

F.  "I'm mad at God because ... (fill in the blank - as many different answers as there are angry people.)

G. Seeing the Corpus on the Crucifix prominent at the front of the altar is a "downer" never mind the fact that He had to die in order to rise for us.  They don't get even the simplest part of the Passion let alone the wholeness of Christ's coming as a baby for us or the beauty of the Old Testament and how so much of it was precursor to the New Testament.

H.  Etc., Etc., Etc.

Good replies, both of you.

I believe one of the main reasons people don't belong to a religion is, as you said, Rajan, obedience and also commitment. 

The word "religion" comes from the Latin religare from which we also get the words "relationship" and "ligament". In seeing this we can see that a religion is a relationship that binds us together, and to be bound to someone requires service; a denial of self for the good of another. And religion directed to God is a relationship that not only binds us all as His children, but also binds  us to God by demonstration in the rites and liturgies. The act of being religious is also the highest form of justice because we are giving to God what is due Him in right worship and we do that by acting in cooperation with our brothers and sisters, serving God and each other in love - the fulfilment of the "Greatest Commandment". This is what is entailed in belonging to a religion: serving, not being served which unfortunately is the motto and mantra of our entitlement society.

It is said that the words of the devil to God before he was cast out of heaven were, "I will not serve".