How you choose to configure homework sets is up to you since you are using the problems in the way you think is best and you are not forcing anyone else to do what you're doing. If you write a pg file (webwork question) that "hard codes" only one attempt allowed, then other people who use that problem are forced to use one attempt (because the option for multiple attempts as set in the homework sets editor has been overridden by a custom answer checker in the pg file). So, "hard coding" the number of allowed attempts is what goes against the webwork philosophy that professor should be allowed to choose how to use problems by configuring the number of attempts in the homework sets editor.
Best regards,
Paul Pearson