This may be a dumbquestion, but Misspriss and kiss, is there a medical reason to refuse, or is it just preference?
Germs can be spread this way, can cause the waters to break early (as in getting checked before labor). There is no reason to have them before you are in labor anyway, because someone can be 1cm dilated and have their baby within hours, and someone can be several cm dilated and not go into labor for weeks.
During labor, they can disrupt your rhythm, they can stress you out necessarily, they can introduce germs into your vaginal canal (this can be bad if waters are already broken). Unless you are going for a epi, they are not that helpful. People dilate at different rates.
If you have not had them before, they can be extremely uncomfortable. The cervical checks in my first labor were the most painful part.
What is the medical indication to have them 1) before labor, and 2) during labor?
I do see the need for a quick check if you are feeling pushy, to make sure you are fully dilated. But checking constantly during labor just makes mom feel she may or may not be going fast enough, gives providers an excuse to augment/insist on c-section which may not be necessary, etc. I can see where it may be needed, but not as a routine thing in labor.