The problem is nobody is going to read them. That's because the people who these scientists are targeting (other established academics, funding sources) choose to ignore the rest of the internet and only read the well known journals. This is almost exclusive to life sciences though. In CS, physics and other disciplines people just upload their preprints on arxiv and don't really bother about impact factors and such.
I don't think most scientists bother much about impact factors. Institutions and funding agencies are the ones who bother about impact factors.
I work in CS and I know that if I want my paper to be read by the community I have to publish in a conference and/or arXiv, as almost no one read journals in CS. But then comes one of the almost infinite assessments the bureaucratic system in my university and country makes me jump through, and what do they look at? Impact factors, and conference publications are worth next to nothing. So I constantly have to juggle between what is good for being relevant and known in the community, and what is good to keep my job, which are often incompatible.
This depends on country, though. In the US, I think the funding agencies have left behind the impact factor fetishism in CS and authors can (and often do) just publish in conferences. But in Spain if you don't publish in journals you just don't get a position in academia, in fact some universities are starting to require > X ISI JCR-indexed publications to be able to become a PhD. And I have heard that in e.g. China it's the same thing.
