It’s not really about the individual. It’s about fashion industry standards.
It’s not like Boden have a range of models with different healthy builds - very tall and very slender is the default (and what modelling requires)
Clothes hang better on very slender models. We like identifying with these beautiful women because we might look a little bit like them when the zany floral patterned pencil skirt is stretched across our size 16 arses.