@MnM156 I have no experience of a labour without the drip, but I am given to understand that contractions with the drip are more painful than those without. However, there is no reason you can't take a wait and see approach to pain relief. That's exactly what I did, and while I needed a higher level of pain relief than I hoped I would (diamorphine), I have zero regrets. The danger is, that should you want an epidural later in your labour, you might have to wait a while, or even not be able to get one at all.
I had a slightly different experience to MsFrog, in that while I did have the regular induction process of pessaries and ARM, I was in no way in labour until the drip was put up. However, I didn't get 0-60 contractions immediately. I needed the drip dialled up to the penultimate max dose before I was contracting strongly and regularly enough to be called active labour. This meant I got an hour or two of build up of labour which really helped.
@Stargazer87 Absolutely bring your own pillow! Not OTT in the slightest. I work within the obstetric department, and every single colleague (including myself) who has had a baby bought their own.
As for reasons for the drip, once your waters are broken, you're at risk of developing an infection. If contractions don't start on their own, the drip will start them for you. If you're contracting on your own, with broken waters, but not dilating/progressing at a suitable rate, the drip can be used to augment your contractions.