The answer to that is simple, the track's unabashed sentiment and charm - for now - has won the jury over. If there's a guide to writing solid, down to earth pop music then I think the sisters of HAIM have a copy.
The fact all this is paired with a killer 80's vibe means the girls are not only creating earthy and grounded pop music, they are doing it with style. Lets not get too ahead of ourselves here though, the band are signed to Polydor so expecting long term substance would be naive. Listen to "Don't Save Me" below.