The landlord is often not the same as the developer or construction company, and sound isolation works best when built in while the building is being constructed. Attempting to retrofit later is often less than satisfactory. So it is often not the landlord's fault, it was the developer or construction company that cut corners and used the thinnest, least sound isolating materials they could to keep their costs down.

Something I've seen with renovations is construction companies not understanding how to attenuate sound, and not bothering to learn or, even better, consult someone who knows.

Well meaning PMs read up on products and throw them at the problem and it's treated as a great success because there are no hard targets, just a general desire to reduce noise, and that happened.