Oftentimes the 5 floor limit is for timber framed walls. In the United States this is due to fire codes and the ability to evacuate buildings. You'll often see two stories of cement construction for stores and parking with 4 or 5 stories of apartments above, or just 5 stories of apartments alone. Larger buildings are possible, they just don't have the return on investment.

There are some interesting articles on the design choice, but it's a bit sad that we've gelled on this design.