I think there is an element of choice involved in how consumed and blinkered you become about parenting and babies. Not totally and there are times when it is all consuming especially when there's illness, disabilities, relationship breakdowns etc
But on the whole, I am fairly impatient with it.
A lot depends on your personality, what support you have, what your partner is like as a co-parent and of course what your babies/children are like so lots of factors.
But, the people I know who have maintained a semblance of their pre-kids life are the ones who have made a concerted effort to do so.
They didn't drop their longstanding friends for their NCT/baby group people.
They didn't turn down every invite because they won't leave their baby with dad, grandparents etc ever.
And they didn't bore on endlessly without taking an interest in their friend's lives.
They also didn't make petty comments every time a friend went on a weekend away, bought something new or went out and did something.
In return I showed a massive interest in their kids, enjoyed hanging out with them, went to fucking soft play and child friendly cafes because that's what friends do for each other. I love them and I love their kids.
Parents who can't do that are on the whole choosing that change and become horribly insular and tedious.