it makes no sense if you think it’s between you and your opponent.
But can make sense when considering a 3rd player .
In battlegrounds there was scandals of players joining just to help someone specific win.
If you see someone play well , but with a specific opponent keep losing , mb you can report it.
In mercenaries there was a month of players wintrading just to open infinite chests , they joined games with 5merc of same color and 1 different , and based of a color scheme you win lose . This players got a huge advantage , they farmed coins easy …
In hs ranked there was case where people wintraded with other to make them qualify for real events , in 3rd part tournaments someone with low ELO can let friend win becouse he has more chances , etc. etc.
It’s hard to proof it , but is possible someone can use it.