Speculating here, but my observations of Dorsey/Square is that they see more long term value in being an exchange for fiat to cryptocurrency rather than (only) being a settlement house for payments. I see them acting as both exchange and clearing house (and debit and credit provider, and payroll service, and...), which, sure, Visa could too, but Square has/is building the infrastructure for those mutual use cases, and Visa is mostly playing catch-up.