Historically, swords were most often worn at the hip in either a sheath or a scabbard. The purpose of a sheath or scabbard was primarily to cover the blade to prevent the wearer from injuring themselves or people around them whilst walking around. It also serves a secondary function of covering the blade to protect it from the elements.
A sword frog however, as far as I can tell, is more of a modern invention and is mainly used by the Live Action Roleplay (LARP) community. Swords used in LARP are typically made out of foam, meaning a wearer does not need to worry about accidentally cutting themselves or about their weapon rusting in the rain. As such, a sword frog does not cover most of a blade as it simply does not need to - covering all of the blade in this context gives no more benefit than just covering part of it. Here is what a sword frog may look like:
So, my question is, for what practical reason might an adventurer in a stereotypical medieval-fantasy setting wear a sword frog?
As there are no archeological findings of sword frogs from the medieval period that I know of, so adding them into the setting would be very anachronistic. Whilst I could simply explain the existence of sword frogs as being a fashion accessory - something else for nobles to decorate or something to show that you own a sword, even if you aren’t currently wearing it - Im specifically looking for practical reasons to justify their existence as not every adventurer is going to care about how they look.
The sword frog may be either used on its own or in conjunction with either a sheath or scabbard - just as long as the sword frog has a purpose and a good reason for being there. For example, most sheaths and scabbards had either belt loops or their own belt built onto them, simply ignoring the in-built belt or belt loops just so the sword frog has a purpose is not a good enough reason.
Magic is not off-limits for this question, answerers are free to use whatever fantastical ideas they can come up with, but I would prefer if the majority of answers focused more on the mundane rather than the magical.
If possible, the best answers should include testing of their proposed idea (or a detailed enough explanation to allow someone else to test the idea), or any relevant experience, to see if the idea would work in real life (which subsequently would mean the idea would work in the fantasy world as well).