It’s not as easy as it first seems. You have to think about what is usually included in an apartment (toilets, sinks, showers, ovens, stovetops, windows, garbage chutes etc) and realise that many of those items will need significant building renovations. Most office suites don’t have bathrooms (there will be one large bathroom in the middle of the building), so separate bathrooms will need to be built for each apartment. No one wants to live in an apartment without windows, so the only parts of the building used for residential will be on the edges of the floor.
It’s not impossible - but it would require an upfront investment that would then demand a higher price for the property.