It's quite useful. For example Brazil ARE the best (refers to the Brazilian football team). Whereas Brazil IS the best refers to the country. Chelsea is good could refer to the place or a person. Chelsea are good refers to the team.
Single sentence utterances like this are rare. In context this distinction doesn't actually provide non-redundant information. So calling this "quite useful" is a bit of a stretch.
It is however generally useful to have lots of redundancy in speech. It can help to sort out mishearings and misspeakings. Similarly in handwritten text.
