Watch the Bends & Vibrato Exercise 1 online guitar lesson by Jeff McErlain from Beginner Blues-Rock Soloing
Playing in tune requires both physical and aural practice. The proper technique to bend strings is one that needs to be practiced, and while doing so you want to concentrate on developing your ear to hear when your note is in or out of tune. This requires a lot of attention over many years. It's important because obviously nobody wants to hear somebody play out of tune, but it's also a way that these techniques define your own musical identity. For example, when I hear Jimi Hendrix play I know it's him immediately, and that's almost always due to his vibrato. It is unmistakable.