For several reasons. I will not mention my own -since I don't want kids myself-, but in general, being a (future) step dad can be very complicated (you're not his/her dad so, who are you to raise that kid?), you will prob see her ex hubby every now and then (not a pleasant feeling) plus it's hard to experience freedom with someone with the responsible task as a parent.
At least, take your time bro and think about the consequences, the positives, but also the negatives.
Well I give you another take on that story.
One of my best friends and workout partner who is Russian (and a Jew lol) is married the third time, this time a latvian woman - great girl.
Anyways, she has a daughter 19 years old and let me tell you OMFG the girl is crazy hot - I am going off topic here but damn first time I saw here I was like - shit I cannot look at her this is his step daughter lol now we laugh about it and make jokes.
But back to the story, I see Yury so many times with his step daughter and she embraces him totally as her friend/father - I mean the whole thing like snuggling up to him teasing etc. and yes okay his stepdaughter is a bit different I mean how many hot 19 year olds with smoking bodies do you know that have one dream but to visit Chernobyl and go urgan exploring.
But it can work.