When using form request classes, it can be really handy to be able to manipulate the request data before running any of the validation rules. This could be to:
Coerce the data into a format the validation is expecting (e.g. convert a list of comma separated values to an array). Cast a value to another type (e.g. string to integer or string to boolean) Account for common user errors, like typos. Remove inappropriate or potentially malicious content from input data.