Dark Matter is not being proposed because any new evidence has been found for a new phenomenon. Instead, it is proposed because an existing package of theory, a formula for how things work, appears to be broken. ‘Uh, oh … Dark Matter, maybe’!
The exact problem that has arisen for science, is that galaxaies out in space do not ‘dance’ properly in the gravatational sense, for what we think they weigh. We look at how much light they give off, estimate how many stars that takes, how much the average stars weighs, then we plug the numbers into the gravity-formula … and it’s off, wrong for how we can see them move. Not by a little bit, but WAY off. 85% of how much they weigh, to dance the way they do, cannot be detected or accounted for. Something is wrong, and it’s not a sutlety.
https://en.wikipedia.org/wiki/Dark_matter
The features of dark-matter proposals strongly resemble those of the 19th C ‘luminiferous aether’. The aether wasn’t supposed to be luminous itself, but to have the properties necessary to transmit light (and all electromagnetic radiation), in the form of pure-waves (without a particle-nature).
So there’s nothing that says, ‘Hey look! Dark matter’! No, instead we’ve found that an important basic formula is grossly wrong, and we’re ‘making up’ a new dark-matter actor – outa thin air, without a speck of evidence that it exists … in order to patch-up the now obviously-defective – but Sacred! – formula.
Known familiarly in other circles as ‘Throwing good money after bad’, and in yet other circles as ‘Digging yourself into a hole’, and ‘Painting yourself into a corner’. Science has proven itself, long-term & repeatedly, to be not-very-clever in this particular regard, psychologically or socially.
Dark Matter is a diversion. ‘Oh look!’, but not at my broken Theory. Science collectively is trying to save-face, protect their core intellectual investments, its status. This behavior can be ‘belled’ in a relatively friendly fashion, by pointing to the similar dodge-ball theories of the Luminiferous Aether. Or, the response could be less-friendly, by pointing to the real costs for both science & the Public, of the 42 year project to uphold Piltdown Man. Realistically, to spare certain ranking scientists the embarrassment of exposure.