Why so many girls here living/been with bf for years but no marriage?

Hey Girlies,

I'm not trying to be a debbie downer or upset anyone. But I'm trying to understand why so many girls here have been in a relationship with their bfs for years but no engagement or marriages? I have noticed so many times, girls have said been with a guy for 4-10 years. Now if you don't want to get married, then completely understand. If they're your high school sweetheart and you're in your early 20's and trying to figure yourselves out I also understand. But those that still are with their bfs and both are now fully mature age, why still no marriage?

Please keep the post coming. I love reading the different points of views! So many that I haven't thought of.