The CPF problem, and why an eSIM sidesteps it
Buying a local prepaid SIM in Brazil generally requires a CPF, the Cadastro de Pessoas Físicas tax identification number. Foreign visitors do not have one, and obtaining one involves a bureaucratic process that is not realistic for a short trip.
Travellers work around this in various unsatisfactory ways — asking a hotel employee to register a SIM in their name, buying from vendors who bypass the requirement, or simply going without. None of these are good options.
A travel eSIM removes the question. The profile is issued against your purchase rather than against a Brazilian identity document, so there is nothing to register and nobody's CPF to borrow. For most visitors this is the strongest single argument for using one in Brazil.