Why are so many young people getting married??

I’m 21, I turn 22 very soon and I’ve seen so many people near my age who become pregnant with their partner before they get married, or get married so soon like maybe a year after dating, I’m actually so curious? I’m not sure if it was just how I was raised but getting married to someone you haven’t even been with long enough to fart next to blows my mind. Why are people so careless about themselves and who they give themselves to?