Not sure, but I think it may be a throwback to days gone by.
Whenever I see an older quilt with hand stitching, I always think 1) it must have been made with extra love; 2) someone with a special fondness for hand sewing or 3) quilter was taught by a grandmother who felt the only way to complete a quilt was to hand sew the binding, why?, because she said so LOL
I machine sew all my bindings with decorative stitches.
The time it would take me to hand stitch the binding, I could finish another quilt top LOL