I'm answering from an HCI-related subfield of CS:
What you describe - attendees print and bring their posters themselves - is completely normal.
While I do not rule out it exists even in my specific field, I have never encountered a conference that would print posters for you. Any time I have participated in, or just looked at the CfP for a poster session, attendees were merely told the available board size (and thus, the maximum allowable size for the poster) and asked to prepare their poster in time for the poster session.
Typically, attendees then have the poster printed at their home institution (and get compensated by the institution as a part of the conference attendance cost). This has the nice side-effect that, at least in smaller places, you might already get in touch with a few conference attendees at the airport, because you notice the people walking around with poster tubes. At some point before the poster session (depending on the conference, already at the beginning of the conference), attendees will take a few minutes to affix their posters at the boards they have been assigned (or just at any boards, if the poster space works in a first-come first-serve manner).
The poster belongs to the attendee/their employer and they are free to do with it after the poster session what they like. A possible procedure that has been followed by many people I have been in touch with is to take the poster back to one's home institution and place it on some wall in or near one's office.
A word on your impression:
The opposite case seems strage, ridiculous even: For 10 or 20 people, coming in from different countries, to each have to arrange for the printing of a poster and either bring it from overseas in a special container or to have to coordinate with print shops in a city they don't know.
In a way, that's true. But then, note that poster printing (well, any graphics printing) comes with a certain deal of variety and "risks". Colours might be messed up, the size/margins might be unfitting ... add to that that different regions of the world are used to (and thus base their poster templates on) different paper formats. Thus, it is desirable to see the poster when there is still some time to make some corrections.
As for the special container - any university institute I have encountered owns several of these, for exactly this purpose. Note that if you want to bring back the poster (as described in my text above), you need such a container anyway for the way back, so there would be no point in carrying the container there without anything in it.