Just to help a lil more with the understanding, the 5 kakkars are more than just exterior references to sikhism
Kesh - uncut hair, not only on the head but all over the body: It is important because kesh represents strenghth and it is stressed that a sikh should give up his life before he ever cuts his hair. Also keeping your Kesh is a sign of "saintliness"
Kangha - Kangha is a small wooden comb: Kangha is used to keep your hair neat and tidy and is tucked away in your distaar. It is important because respect for ones body is a theme throughout sikhism.
Karha - is made of iron or steel only. A karha made of gold or any metal is considered an ornament: It is important because its meant for restraint and gentility is also a reminder that the Sikh is forever bonded to the Guru and it reminds the wearer to always do the right thing
Kirpan - Sikh sacred sword. "combination of two words: Kirpa (mercy) and Aan (honour). Thus, the Sikh Kirpaan means: "the defender of the honour of a being".": It's important because it's an emblem of courage and adventure, also of self-respect, prestige and independence. It is supposed to be used only for self-defense or for the defence of the weak and innocent.
Kachhehra - drawers stiched a certain way: It's important because it reminds the Sikh of moral ethic, restraint and control, chastity.
What makes the 5 Kakkars important is what they represent. Im assuming that most people feel that they don't need the 5 kakkars to remind them of how to live life morally, which is completely fine. Nothing wrong with that. The thing is SIKH, the actual word, is defined as a student of the Guru. If you do not want to practice what the Guru teaches, which includes the 5 kakkars, than you really need to ask yourself why do you call yourself SIKH? It is written "Rehat Pyaari Mujko, Sikh Pyaara Nahin" which means a Sikh by name is not good to me a Sikh by definition is of use to me.
And finally, Sikhism isn't about being birthed and following Sikhi exactly from the time you can walk. Sikhism is all about the journey, the path. Theres nothing that one can do and think "well, its too late. I guess i can't be a Sikh anymore". Everyday is a new day to start the journey and choose a new path. So if someones hair is cut, or they drink, etc, that doesn't mean that they can't start following the teachings and practices of the Guru.