I want to to start this off by saying, this is not a pro ban or no ban argument in any way shape or form, I'm currently indifferent on the banning of smeargle, scolipede, and baton pass. I'm only here to try and get everyone on the same page by giving what information I know.
Now on to my actual post.
First off, it seems to me that there are a few reasons behind not banning smeargle and scolipede. One of them is the fact that they are both BL. They're not meta game defining, simply because very few people use them, it seems strange to ban something that's not meta defining because it makes it seem that they aren't broken, after all if they were, why aren't they used as often as proven non-broken pokes?
Now, the next reason is a little more complicated. It's the fact that smeargle and scolipede are so different from every other banned poke. The style of baton pass makes them different and therefore people don't know what to do with them. Most ban arguments are supported by arguing that they are similar to other banned pokes, like in the recent greninja ban people argued it was similar to mega luke, but smearle and scolipede are different; no poke has been banned solely for the use of baton pass, and no other banned poke is so weak. And it seems to me that that's the reason people want a complex ban. This is different from speed boost+blaziken and protean+greninja because smeargle will NEVER pull off a sweep on his own, scolipede will NEVER (well I guess it might, it's stats aren't that awful) pull off a sweep on his own, and by looking at the viability ranking of OU, you'll see that the criteria is based on the team support a pole needs. Smeargle and scolipede are that team support. They don't destroy the meta, they give other pokes the power to do so.
Now, the reason people don't want to ban baton pass. Baton pass is one of the few moves that has several uses, stat passing, pursuit escape, and momentum gaining too name a few. Most moves only serve one maybe two purposes but even in that case the two purposes are heavily related. The argument for not banning baton pass has the example of drizzle+swift swim ban, and I would like to delve a little bit more into why this is similar. Rain also has multiple uses, negating the thunder and hurricane accuracy check, boosting water moves, and swift swim and other rain boosted abilities. We decided that although one of these were broken, that not all of them were, and that these uses for rain were different and important to the meta and therefore we decided on a complex ban. Because rain was diverse and different. Just like baton pass.
Again I'd like to state that I'm neither on counter-ban, nor am I on pro-ban, I'm simply stating the information I've found.