If a commercial space is owned by the landlord free and clear, then the landlords have zero incentive to rent it to collect smaller than desired revenue unless property taxes are so high that the landlord must lease the space to at least cover the property taxes. If course that means that the rents skyrocket for all properties as the property taxes now eat majority of the rent.

If the landlord has a fairly regular commercial mortgage, it is probably IO + balloon in 10-15 years. The landlord's bet is that the property would appreciate enough that the landlord can refinance it for the next IO + balloon, kicking the can down the road for another 8-10 years. Pretty much no one operates commercial buildings with the idea of paying off the loans on them, which is why as long as the real estate continues to go up in a long term it is makes sense not to engage with small time tenants. The only time landlord has to engage with small time tenants is if appreciation of the property won't create enough equity to refinance the balloon payment.