I personally believe that everyone should practice psychic self-defense...not just because of negative "entities" but because of negative "energy" in general. You do not have to be on a journey of new age spirituality, to necessitate and benefit from using psychic self-defense.
the mere act of it, can have a placebo effect that carries over, and helps you to deal with other negative events in life, because you feel like you are pro-active in protecting yourself from the effects of anything negative that comes your way. Some people, just need to feel empowered to feel safe. If you're one of those people, than psychic self-defense can help you, even if you are not seeking a deeper spiritual meaning in life.