Lottie - in some people (such as me) they cause horrendous thrush. (I can't use anything scented on my nethers).
They can also cause UTIs by irritating the urethra.
People who are allergic to other scented hings, such as washing powder can have a similar reaction in their nether (mmm, genital rash).
They also smell really obvious.
You probably aren't the only person who likes them or buys them. However they are becoming increasingly common and it can be hard to find unscented ones. So for some people, not only do they have to suffer cramps, bleeding, spots, PMT etc but they also have to put up with itchy bits, rashes, UTIs and smells they don't like.
If they work for you then great, anything to make AF easier! But if you do find yourself getting any of the above, try changing to unscented!
I'm now on cerazette so no periods for me (mahoosive thanks to the inventor of that one) but before I used a moon cup or lil-lets, which thankfully remain unscented.