Most people will not bet on friendly matches because it is not uncommon for coaches to try to rotate players and usually will be given the opportunity for young players to undergo the match, so the results of the match can be beyond predictions and as a result people will lose money on the bet because the prediction of victory may change From the bet that is installed. But if the quality of the two teams is very different, it is certain that the match will be won by a team that is much stronger and has a far more experienced player.
When facing Basel Thomas Tuchel tried to replace all of its core players in the second half and that was why they had to receive a draw in the match. Aseko equalized in the 70th minute and was still fortunate enough to avoid defeat even if only a friendly match.
In friendly matches, sometimes a team will not appear with their main players because the coaches of course give rest time to their main players to maintain the players' fitness and also avoid injuries during friendly matches. So it is not uncommon for coaches to play second tier players to give them playing minutes and also be able to monitor their improvement in quality. Yes, I agree with you that in friendly matches it is wiser not to place bets because the opposing team may perform better than them.
I think some people are sometimes able to read the conditions in terms of the game that will be arranged by the coach so that they will be ready to try their luck in the bets they place. Well, even though sometimes the odds are very attractive, I don't think that's a strong reference for betting on friendly matches if doubts surround our feelings.