A Chrome/Firefox user expending some effort to make their existing extension available to Safari users is doing those users a favour. Generally one doesn't have

A Chrome/Firefox user expending some effort to make their existing extension available to Safari users is doing those users a favour. Generally one doesn't have to additionally start donating money to someone's preferred charity when already doing them a favour. You're going to have plenty time to Wrap Your Head Around this dynamic by simply observing how the Safari WebExtension ecosystem plays out.