Your information is too vague. Are you shooting enough energy to adequately shoot a mechanical?

There truly is no reason to not shoot a fixed blade head. With a properly tuned bow, matched tune arrows, fixed blades will and do fly with field points so accuracy is not a reason to shoot mechanicals.

So what are reasons....well shortcuts to a poorly tuned bow, poorly tuned arrows...possible larger cutting diameter depending on model....

Yes they can and are effective, just be sure of the reason you decide to swing towards mechanicals and not a quick fix for bad equipment.