Moving onto my new role and observing things from a different light, I think it’s interesting how certain common day areas/ items have unintended secondary purpose (for better or worse).
An interesting example would be the passenger services at every station. Apart from the intended use of addressing passenger questions this normally serves as the meeting point for most folks. (Most stations only have one passenger service and it is easily identified). In the event there are two passenger service booths, the person setting the appointment tends to name the train line (green line passenger service or purple line passenger service etc)
From observation the secondary use of the space or item leads to a deterioration of the original intended purpose. In this case, the passenger service may be overcrowded by random folks who are there just to be retrieved in a lost and found box. These problems do not really present themselves in the original design process and can only be fixed later on. (In the case of the train stations, some stations build meeting points, at least outside Singapore, I have not seen these locally
Some unintended secondary purpose may not disturb the original purpose. An example is actually barriers or walls used for advertising (or resting):
The secondary use of barriers is an ingenious way to monetize existing features. Design should try use existing resources and assign multiple purposes. It is an amazing step forward to be able to use the same item for multiple use.