Web-only - do I need a separate image for each container?

Thanks for taking time, for trying, however.. it’s not what I’m asking.
I’ll try again, pardon me if I fail.. again
When I:
→ $ ./launcher bootstrap a.forum.xyz # or similar
then process creates:

-> $ docker images
REPOSITORY                        TAG                 IMAGE ID       CREATED        SIZE
local_discourse/a.forum.xyz        latest              d7a7b6509811   2 hours ago    4.19GB

and that happens with each & every launcher ran for a different/new forum.
So I end up with multiple image of the same discourse - is it only me & result should be different?
If not just me & that is desired & expected result, then that is - sure I am not devel and have no knowledge of the process(es) involved - rather really extremely wasteful (perhaps particularly with web-only container) - no?

What I was hoping for - when first tried discourse - what I expected was, pretty much what everything else, every other software which is dockerized does, namely - get that one image and run many containers off it. Is discourse not cap/able of doing that?