Participation in post-compulsory physics is a matter of longstanding concern from economic and equity perspectives. The current study draws upon Bourdieu's theory of social practice, particularly notions of the 'cultural arbitrary', to explore what insights into post-compulsory physics choice might be provided by students who chose other sciences. Utilizing survey and interview data from Year 11 (ages 15-16) students in England, findings reinforce the key role of individual aspirations in subject choice. However, they also highlight the influence of the cultural arbitrary of physics (e.g. as difficult, masculine), leading many students to conclude that physics is not 'for me', hence choosing other paths. This finding emphasizes the entrenched nature of the challenges to increase equity in post-compulsory physics participation.