Conferences can be truly wonderful, but not a universal replacement for publishing.

If you think journals are expensive, try sending your whole lab to a conference in another country. That may not let you in. Where some of the attendees have to fill out paperwork before talking to a foreign national. (does that ever make for awkward small talk...)

For all their many faults, journals provide access to a really wide audience, and- in theory- make it possible to form connections who wouldn't be able to meet directly.