BzJJ:
Because my briefings (drill reviews) include words such as: "for any problems up to V1 you decide and (if) calling STOP have the controls...". The decision that RTO is Captain's-only game had probably been made after having considered the experience/capability/liability/authority issues. If other operators reach a different conclusion, that's fine with me however my job description prescribes otherwise.
Yours,
FD (the un-real)