That's the expectation in a lot of industries (finance, consulting, law--heck my dad works in public health and he's worked 60-70+ hours most of his career). I worked at a big law firm in New York, and most of the partners had kids. Indeed, my daughter was born a month after I started at the firm. I immediately got put on an internal investigation, where the client was under threat of getting their stock delisted unless we made its auditor happy. It was a "if you're awake, you have to be in the office" situation. Somehow we all managed, despite several people on the team, including the partner, having small kids.

I think the attitude towards kids in the tech industry has more to do with its general youth worship. There's a big attitude shift towards kids from early 20's as you go into early 30's.