It's true that having a child forces any responsible adult into revisiting their priorities, and some things that seemed important before parenthood suddenly aren't. I don't think it eliminates a desire to be successful: I think that it changes the parameters by which you determine success.
And having a child throw up/mess on your nice clothes and shower the inside of your nice car with food and toys tends to make you settle for less in those departments, I admit.
Prior to kids, I considered success to be pulling down a six-figure salary, having a nice big house and my own office at a high-profile, successful company. Now? Success is having a quiet office (size unimportant but preferably my own), enjoyable work and time to spend it with my kids before they are old enough to leave home.
It is worth it, and anybody without kids who says otherwise knows not of which they speak. Parenthood is the difference between knowing the path and walking the path. If you're not a parent, you've just read the brochure.