I pretty much have the exact same thoughts on flap discs. For years I have always wondered why people think they’re so great. They are typically expensive, are only good for about only the amount of grit that is exposed (I much prefer a hard disc or fiber disc), they tend to dig when you don’t want them to and make a lot of nasty dust for not doing much work. The best use I have found for them is de-burring edges and I don’t even really like them for that. The next best thing is if you have to round an inside corner.