Is it bad to have a child out of wedlock?

Why do some people consider having a child out of wedlock bad? I'm not a devout Catholic and neither are my parents, but my parents are very traditional and old fashioned. They grew up in the 50s and 60s in Panama. They think having a child out of wedlock is bad and i know they'd be disappointed if i ever did that with my bf. I'm in my 20s and i live with my bf of 3 and 1/2 yrs. We do plan on getting married in the near future and i do want to have 3 kids with him. I was raised to get married first and then have children. I don't really have an opinion on this topic, but i guess i was raised to think of it as a bad thing.