Personally, I think the wifi ratings are interesting and a great way to help get people to do business with you and vice versa. It works alot like how Ebay does for when a seller leaves feedback for the item they've bought. Imo, it helps show how trustworthy the buyer or seller is and instead of just trying to "guess" on whether the person is nor not, the ratings help make a decision. Some people forsake them and do not care about them, and that is fine and all, but I on the other hand, like to show that I care for the person I am distributing the item for, so that they come back to me when they need it. It is how people keep their "customers" when doing business. Whether you call selling items, clothes, or whatever on Animal Crossing a "business", I find it a tad bit far there, but it does however help both parties on each end feel comfortable with a mutual agreement that each can be trusted. Personally, I wouldn't want someone with terrible feedback to serve me and vice versa. I would be afraid of getting "ripped" off and that would just be a waste of time. I also love to help send positive word around for the ones that deserve it! It makes you feel good, and makes them feel good as well. Same for if a person who being misleading or so. I guess most people don't leave much feedback sometimes because they really don't take into account how much help it actually can be.
In fact, just this morning a person went onto my profile and had decided to leave false-negative feedback just because of all the positives ones I have had accumulated. I didn't even know this person nor did I have any wifi trades with him at all. He just plain felt like trolling around and then tarnished my perfect record with false information. I was pretty upset to say the least as I'd not want people seeing my feedback and to then think that I was "mean" or "rude" I have reported him to the mods so hopefully something can be done about that. But yeah, that is basically my intake on the matter lol