The 13th salary exists in other countries too (example: Switzerland). It's a dumb thing to complain about because you have to be able to pay an employee's yearly salary in a year. It's not a surprise. It comes every December.

FGTS also has its equivalents in several forms of unemployment insurance. It's a bad thing only in how the insurance is mismanaged by the government, not because it exists at all. I guess countries that do not have unemployment insurance are rare and extremely poor?