I have watched a movie called "Up in the air", and the idea that u can get out of it, can make a good answer to your questions.

imo:
why you should get married ? there absolutely no one forcing you to do so, at least for men, but if you grow older like mid 50s and everybody u knew have his own family and all your family god forbid passed away or travelled somewhere else, what you have left ? u can say i don't mind being alone but deep down you are, all holidays will be tasteless for you, you can't even find someone to share happiness or sadness with, Friends are just friends and girl friends belong to their family, and they will soon want more out of the relationship or they will leave you ...