I think it was to try and appeal to the hippy audience. Also at the end of the bike ride as Newman is crashing through the bull's pen she is up in the hay loft, was she getting ready to make love or had they just finished?
I think it was a really campy way of showing that they have affection for each other. But it does look so out of place for a film like this.
Sometimes a movie or tv show plot is so stupid that only the stupid can understand it.

The "raindrops keep falling on my head " scene is so absurd that I have no idea why it was put in the film . It was camp and definitely stopped the film from being taken seriously .