Why do people act negatively to young couples?

my bf and are pregnant with our first and people are saying your too young to settle down you should live a little or hes going to bail. why do people have to say negative things and not be happy for us i am 19 and hes 22 we've been together for almost four years and we've been through alot so i know hes here for the long haul why can't they just congratulate us on starting our families yes we are young this wasn't planned but now that we are expecting we could be happier and we want to be the best parents to our child we can be how do we show people we are doing the best thing and not going to be another statistic. Neither of us plan on me quitting school since education is important thing too me. we are going to make it work. He has a great job in the military and we are planning on getting married in may. help.