I find it very impolite for an employer to not give any follow-up response to a job seeker after receiving a CV/ after a job interview.
When I was in the position where I remotely interviewed a freelancer, I felt somewhat different, though, when I decided that the given freelancer was not my match. I tried to analyze this feeling prompting me, "it just doesn't fell right to tell the freelancer "I took a look at your portfolio and for the time being I would be looking for something else". That sounds somewhat rude or more precisely out of place - even, though it carries the best intentions to inform the freelancer whether s/he could rely on my gig or needs to continue searching for work.
What I came up with, was that a freelancer, by definition, always has numerous options and resembles a commercial service, a micro-enterprise, unlike the full-time job candidate. That is to say, that the freelancer would be considering other clients in all cases, no matter my decision. This is not the case with full-time job seekers, of course, if they are about to get hired for job A, they should not negotiate for job B, because they may get in the confusing situation of getting proposed job B, before job A, while A being their top desire.
Therefore a freelancer is not really dependent on getting my reply for earning his or her bread. Just the way you do not inform the shop assistant at a given outlet that you chose trousers in the next one, so they better not expect money from you today. It would sound silly above all.
This is what my analysis is telling me, but I cannot be sure. What do you think?