Floor fitout is typically left to the tenant, not the landlord. Building skyscrapers with empty floors gives flexibility to future tenants, increasing the rental/purchase value.

Tall office buildings may often have open plan, but this should be attributed to the fitout builder’s client (e.g. SomeCrazySoftwateCompany as the incoming tenant), not the building builder’s client (e.g. SomeGroupInvestmentCompany the owner of the building)