Musing absolutely does curate answers. There are, however, a few reasons that you may have noticed some answers gone uncurated.
1. Musing curates our questions and answers manually. This means that there are real live people going through and doing the curation- not bots. I don't really know the ins and outs of the Musing staff but I'd imagine that at the time being it's a small enough group that this is not a 24/7 service. I've often noticed that after spending a lot of time on Musing and answering a lot of questions that any votes I might get from Musing all come in at once hours later- meaning that it was a few hours before someone went through and curated a large amount of stuff.
2. They may have simply not gotten to it yet. Like I said before, it is not a 24/7 service. Especially as activity here builds, they are going to have some gaps while they are figuring out how to work with the growth. I see a lot of repeat questions asked on the site- some seem to be just copy and pasted from other users. This is the type of thing that is not going to help.
3. They aren't good answers. If the answer given is irrelevant or unhelpful, there is little to no chance that the author will get a vote. Going along with the manual curation- there are real live people checking these answers. So in order for someone to give a vote, they will want to ensure that people are using the site correctly and actually providing real help. Sometimes I've seen answers that are just clearly copy and pasted from the web or even Steemit's whitepaper. Often times it's so obvious that it sticks out immediately. I've even gotten an answer in a completely different language. Obviously, it did not receive an upvote.
4. They simply missed some. They are human- it's entirely possible. And it's nothing to throw a fuss about. There are a lot of questions and answers coming through here every day. It's up to us to make it easier for them to curate. What I mean by that is that everyone needs to use the site correctly. All the copy and pasting and other BS going on doesn't help whatsoever. It provides more for them to sift through and makes it harder for them to reward us.
I'm sure there are other possibilities that I might have missed but I hope this is at least somewhat helpful. Cheers! :)