On the one hand, it could be a good opportunity for one family to go on holiday somewhere away for some days and that want to be sure that there is another family who they rely on that is looking after their house while they're on holiday as well . They can enjoy a new place, and know a little bit more about another environment.
On the other hand, you you have to make sure that you exchange your house with a reliable family in order to know for sure that you will take care of their house as the other family will too, because if you don't know what the other family is like, it could be a complete disaster and then you might regret your decision.
To sum up, I think it's a good idea to make a house exchange on holidays, to live a different situation than normal for a few days, but in my case, I don't think I would ever swap my house for a holiday, because I would get worried to be careful all the time not to break anything in the other house, and I don't like other people to be in my house without my presence because I would feel uncomfortable that another family that maybe I don't know, is staying in my house.