I would estimate that 80% of my married friends sleep in separate beds and their children sleep with them, up until around 8 years old. Then one of the parents gets the boot to the couch. I know know maybe 2% of my married friends sleep in the same bed. The rest don't have children, and still sleep apart either because they don't live together or because they don't cosleep.

I have friends that are married happily (genuinely) and live next door to each other. For real. And the 7 year old son sleeps in bed with mom.