First of all, features can be a standard without (full) FF and/or Safari support.
Second, Safari has a monopoly on iOS and controls what other browsers can support on the platform (that also usually means "less than Safari", because SF gets to support things first). They are in a unique position to hold back the entire web, even on other platforms. They're holding the standards hostage by not allowing the market to decide which features are important to them (and put pressure on Safari and FF to implement them)
Second, Safari has a monopoly on iOS and controls what other browsers can support on the platform (that also usually means "less than Safari", because SF gets to support things first). They are in a unique position to hold back the entire web, even on other platforms. They're holding the standards hostage by not allowing the market to decide which features are important to them (and put pressure on Safari and FF to implement them)