There's a NYT article on the challenges about this from a few years ago: So You Want to Turn an Office Building Into a Home? -- Here’s How to Solve a 25-Story Rubik’s Cube https://www.nytimes.com/interactive/2023/03/11/upshot/office...
You can think of class c office space, broadly speaking, as oil wells that have very little life left, and get bought up by folks who intend to extract the cashflow until they dump the externality on the public government and taxpayers (like abandoned shopping malls).
A recent example in St Louis is the AT&T office tower [1] [2].
[1] One of St. Louis’ tallest office towers, empty for years, sells for less than 2% of its peak price - https://www.costar.com/article/642008108/one-of-st-louis-tal... - April 10th, 2024 ("Goldman Group buys 44-story former AT&T office tower for $3.6 Million")
[2] St. Louis office vacancy hits all-time high [21.2%] as major companies downsize their footprints - https://www.bizjournals.com/stlouis/news/2026/01/15/office-v... - January 16th, 2026
(conversions when the economics pencil out, haircuts for investors when they don't and more investment is needed to wholesale replace a structure)
US office vacancy rates chart supposedly pulled from Moody's: https://old.reddit.com/r/charts/comments/1p8mhmq/us_office_v...
There should probably building code changes to ban the latter type of office building, and keep the space more flexible and convertible to residential. A big plus is the resulting office space would probably be nicer to workers.