Autoloader is pretty handy, but not open source. That is one reason f.e.
Another reason is f.e. if you cannot guarantee lexicographically generated files, or you do not want to use streaming, or you do not land your raw data into a data lake (read from db directly f.e.).
I still use a lot of batch processing using /.../YYYY/MM/DD directory structure without autoloader.
Not because I donยดt like it (I do use it for new setups), but because at the time it just did not exist and for a 1x/day batch job autoloader is not necessary.