Apartments were added to be a solution to completely unaffordable housing for new and even long-time players. Due to labs making them high value as it was a massive property with low cost, the prices skyrocketed and completely negated the point of apartments and any realm of affordability for low-cash players. Further down the chain, the amount of labs increased to a level that was unpredictable, directly causing and encouraging far more people than intended staying inside their labs and not interacting with other players.
Obviously isolation is how a cook works IRL, but IRL 50% of the population isn't cooking for their entire day in an apartment building where the fumes would be seeping into the upstairs neighbors' apartment.