Why string quartets are important in music

Most musical ensembles have a variety of tonal color in their make-up. Even choirs' sounds vary depending upon the words they are saying. However, in a string quartet there is not much variation in color. Just a string sound. Maybe some pizzicato thrown in. So, the composer has to rely purely upon the music itself to make the composition good. Therefore, writing for string ensembles is in that respect more challenging than for other groups. It reveals very quickly if the composer can compose.