Poste restante was certainly a thing in the real world when I was travelling, and when I lived in the serious Outback, and may still be for all I know. I think it may still be available in Australia, certainly it is in the Outback, in small-town post offices such as in the little bush town where I now live, or general stores that handle mail for their local areas. Whether this is just country tradition or whether it is still the usage in cities I do not know.
The
entry on Wikipedia's page on poste restante actually has something to say about that. In fact, glancing at the other entries in the per-country list, it seems to be a service that
usually gets offered
throughout a nation's PO system, rather than only in hotspots (rural areas?) requiring it.
It also mentions that Finnish
Posti is running such a service now, so I assume that
that's why the lone Travel Bureau office in Helsinki stopped offering it. Though I suspect that a
poste restante offer to
Tourists may well set itself apart from
Posti's offer by a longer retention time than 14 days ... It seems quite interesting to compare the retention periods in various countries, too ...
I suppose one day people may eventually look the same way to that odd habit of people (mostly from the previous century) writing actual letters...
I
do work in the "hybrid mail"¹ business in Germany and have to admit that I had no idea that Deutsche Post has a
poste restante system running ...
¹ "Hybrid" because companies shove their outgoing mail to service providers
electronically, where it gets preprocessed², printed, enveloped, confirmed back to the sender, and sent on its merry way, to be received
on paper.
² As in, checked for deliverability (will the recipient address sit properly in the envelope's window? Are the parts of the cover page where the printing provider needs to put his additional barcodes left white?), consolidated (multiple letters to the same recipient are made into a single sending, potentially reducing identical supplements to only
one copy), channeled specially (recipient recognized as someone who can be reached by different, usually electronic, means),
Restmengenfüller (add other supplements as the weight limit of the postage class permits), drop a copy into the sender's archival system, ... - our main business.