A lot of players wait until they're finished and if you know anything about Crosby, like even just surface level shit as a non-Penguins fan, you'd at least know one thing about him - his dedication to the game.
So it makes sense he doesn't want to commit to a family that he wouldn't see often because his career is #1 to him right now, I would wager his final year or two when he's really about to pack it in, he'll get married and the kids thing if he wants it, will come after. Crosby for the years we Pens fans have watched him, has been one of the hardest workers on and off the ice, his dedication to the game borders on the crazy side for how hard he trains, his charities, etc. There's a reason a lot of players say things like it's unfair to their wives and kids to do this or that and that it's time to be a Dad and Husband for a while, the travel, training, etc...it's a lot for someone to do alone while their partner is off half the year playing and training.