Why do guys talk about getting married and wedding plans but keep waiting to propose?

My bf has been talking about marrying me for over 4 months now but still no ring. I am trying not to pressure or rush things, as I know it is not a pleasant experience for the guy's side of it and I want it to be his idea, not me pushing him to do something he might not want to do. However, he has brought up the subject of marriage and having children together all the time, without me bringing it up. So why hasn't he proposed yet then? I don't want to get impatient and I do love him more than anything, but I am wondering if he is leading me on and I am 32 years old and still never married and getting tired of playing the waiting game. We have not been arguing or having relationship issues. We get along really great and both of our families like us together. I am a good person and no I don't nag him about it.... just wondering about things.....