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Our point of contact, the sounding point (the ‘groove’ that the bow plays in), is constantly changing as it adapts to changes in musical context. For instance, when we play strong, loud passages with a slow bow (as in bar 5 of the third movement of the Franck sonata) then we play very close to the bridge, say at Soundpoint 1. You can practice exercises to develop this ‘groove’.
When we play with a fast bow speed and a more transparent texture (as in bar 88 on in the first movement of the Debussy sonata) then we usually play closer to the fingerboard, say Soundpoint 5.
On of the variables that is often overlooked is string length, that is the higher up the string that we play, the shorter the length of vibrating string and therefore the closer to the bridge that we need to play to maintain a clear sound. Bars 10-14 of Kreutzer No.3 gives us a chance to practice varying the point of contact mainly because of the length of the string, that is, the tone colour is fairly constant, so we can focus on gradually playing closer to the bridge as we shift higher and gradually further towards the fingerboard as we shift lower.
Not only does a good enough point of contact give a clearer sound, but it helps maintain secure intonation. A mismatched sounding point and string length can even bend the pitch of the note, and it will quite sound out of tune.