No, this feature should not be removed. I personally use it and I use it for the exact reason that Nir mentioned years ago. If I don't lock my files, I get random people with nothing shared downloading things all day. I am not your free leech server. I've seen enough people with nothing shared, absolute garbage shared, single empty folder shared, etc., that I now use this. Policing uploads all day because of these people is not feasible. You guys want to complain about something, complain about these people who actively and knowingly contribute nothing. They are the reason people lock their files. I feel bad about the people who are general contributors and can't download without asking to be on my list. But this is the only truly effective way to deal with the aforementioned.
Now, I understand that there are also pretentious people who abuse this feature. I've dealt with them myself. They think you either need to have something they want or provide some other form of compensation before you get on their exclusive list. There are also people who somehow have their upload slots set to 0, or their upload speed set ridiculously slow. Removing locked files is not an appropriate solution for anything. They'll just use one of these other things or figure out something else. If locked files are removed and there are people who REALLY don't want to share things, they're just going to make their shares completely private, close Soulseek all the time, just not share at all, etc. Basically, it wouldn't solve anything.
Again, my largest issue is all the people sharing nothing (or virtually nothing/trash). Try addressing that issue and maybe the locked files issue will be improved.
People always think things have such simple solutions "I see locked files; I don't like locked files; locked files should be removed" when it's often not so simple.