I have a couple of Fibrax swabs that I keep in my riding pack, although I’ve only had to use one in about five years – was glad I had it, though.
For general maintenance, it makes more sense to me to get a bottle of IA and use a cloth. The swabs fall apart quite easily when used on a brake rotor. It’s worth bearing in mind that you should really only clean a rotor if it has become contaminated with oils. Mud/dirt will be removed/obliterated by using the brake. IA isn’t essentialas hot soapy water (and rinse) will remove brake fluid; but it does have the advantage of being a much tidier/drier way of doing it.