Why prefer prime-cut sausage over MSM sausage
It's probably simple marketing.

People like the idea of eating 'prime' meat more than 'scraggy' meat, and tend to assume it makes for a better taste and texture (even when it might not).

This is probably the same principle behind things like high meat and low fat sausages - people buy them because they fear 'mystery meat' and anything with cheap content, even when that cheaper content is better suited - such as fat and rusk keeping sausages moist and soft.