Why TTC?

Just curious as to why different people are ttc. Everyone's reason varies. I know a lot are happily married & ready to start a family. Some not exactly. 
Honestly I didn't want kids before, then all of a sudden one day something just came over me & it hasn't gone away since. 
I wanted kids when I was young but for the wrong reasons (a phase) so luckily it never happened & then I changed my mind & for the longest didn't want kids. Now I feel like I'm ready & this is what I want! I Don't know if kids are in Gods plan for me but I've always been weird about the timing. I don't want them after 25 so it's kinda now or never at this point... What are your thoughts on this?