In the US, when you start to get to planning to have a larger family, especially the size of family that would necessitate 4 bedrooms (multiple children, or maybe having a parent live with you), most people expect to move out of an apartment building into a house anyways (maybe detached single-family home, maybe duplex, maybe condo). So there's just not the demand for 4-bedroom apartments or even 3-bedroom apartments to a large degree.
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In the US, when you start to get to planning to have a larger family, especially the size of family that would necessitate 4 bedrooms (multiple children, or maybe having a parent live with you), most people expect to move out of an apartment building into a house anyways (maybe detached single-family home, maybe duplex, maybe condo). So there's just not the demand for 4-bedroom apartments or even 3-bedroom apartments to a large degree.