Here are my thoughts on internals for no clinical reason:

1. They don't give you any useful information. You may walk around effaced and 3cm for weeks - it doesn't mean anything. You can be long and closed on Friday night and in full labour on Monday morning. It really doesn't mean anything. You might be elated to find out you are a bit dilated, but then still be here three weeks later. That is terribly depressing.

2. It has risks. When you are dtd with your partner, it doesn't generally involve lots of poking around inside the cervix. Before labour, your cervix is quite posterior and this protects it from some of the excesses of intercourse. There is a small risk of infection with an internal, a risk of premature rupture of membranes, and as someone said, it can also be the beginning of a cascade of interventions (even if that is just, "Well, you are really ready to go, why don't we break your waters if you aren't in labour by your due date?").

3. If you are already having a lot of Braxton Hicks, an internal can stir things up uncomfortably, even for days afterwards, leaving you mentally and physically more exhausted, not to mention kicking you into that high gear "is this it????" mentality that makes the end of pregnancy so difficult!

4. It brings medical management of your pregnancy and labour just that little bit more to the fore. For many women, it's really important to avoid that, to keep the mindset that the body is doing what it needs to do, and doesn't need checking or measuring or feeling up by a third party to make sure it's performing correctly.

(As an aside, I always get a bit frustrated when I hear about doctors doing internal palpations to "check up whether anything is happening" when a woman is threatening premature labour... way to stir things up if they are happening, or increase the risk of a PROM in the case of an inevitable labour. Use a speculum exam to check for dilation or an ultrasound, for goodness' sake!)