Does sharing the same bed w/your partner help in strengthening the relationship?

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I was once told about a young couple who have been together for almost 3 years. Before they had their child, they slept in the same bed but a few months after their kid was born, they stopped sleeping in one bed. This all first started when their kid was growing and space became little so the husband had to sleep in another bed but on the same room since the house had only 1 bedroom.. and then they moved to another place which had a bigger room, but it had become a habit that even until now I was told, they don't sleep on one bed still. Their kid I think is already 3 years old, which I think is old enough to sleep on his own, but then since the kid is already used to sleeping with his mother, he gets angry when the father would sometimes lie down on their bed because the kid now understand what ownership means.. father has a different bed while he and his mother has their own. It just me wonder how a young couple could form that habit when normally couples are supposed to sleep together. Do you think this habit would help create a gap between them or is this something they need to ignore. Do you think this is normal?