Two worlds (Score 1)

There are two worlds of scientific publishing, the non-profit publishers and the for-profit ones. They have different motivations.

The non-profits' mandate is to further scientific knowledge by aiding dissemination. Many don't charge authors to publish their papers, some ask for covering of publication cost (usually covered in the research grant). If you opt not to pay you will be placed in a queue since there is a page budget for free articles and your paper may be delayed for quite awhile. In principle these journals see nothing wrong with online dissemination (after the paper is accepted for publication and reviewed).

Some disciplines like physics have pioneered in putting up preprints so that work can move forward more quickly. The journals don't regard this as prior publication. The non-profits don't charge much beyond printing and overhead costs to the libraries and much less to individuals.

The situation is a bit blurred for those journals that accept advertising, especially in the medical field.

The for-profit publishers charge thousands or even more for a year of a specialty journal. They don't charge authors but they overcharge libraries. They are, of course, reluctant to see their market undermined by online publication. These journals have gotten so expensive (and there are so many of them - especially in biological sciences) that libraries have formed consortiums to share copies. The for-profits are not doing a service to science, only their bottom line.