Being able to identify which chord(s) is being played within a bar has numerous benefits. An issue that arises from learning scales independently of a piece of music is scales are often never linked with a piece! If you can see the link between a certain scale and the phrase or section muscle memory will kick in and your mind will switch automatically into that particular key. This creates technical fluency and a tremendous ability to sight-read any piece of music. The other advantage is that by identifying chords within a bar of music you are fine tuning your ability to improvise. Knowing instantly which chord fits with which scale is a key skill required to improvise fluently, especially when first starting out.