That is the essence of sanatana dharma - to lead a life of dharma; better still to strive to lead a life of dharma. There are samanya and special dharmas, and as Bhishma said, sometimes it is difficult to decide whether a particular action is right or wrong, or which dharma is to be adhered to.
Marriage according to the Hindu Dharma is to fulfill the four fold purusharthas (four aims of life). Dharma (here it is adherence to natural law), Artha (pursuit of economic well-being), Kama (fulfillment of desire) and Moksha (to liberate oneself). I feel that Individuals who are driven by the primal urge of propagation, fear any one of the purusharthas except Kama, prefer not to enter the Social and Legal commitment of Marriage.
Regards,
Brahmanyan,
Bangalore.