Personal injury protection (PIP) or medical payment are similar to bodily injury liability but instead cover the costs of injuries to yourself and any passengers in your vehicle. You certainly don’t want to be underinsured when it comes to your own medical attention — choosing PIP helps protect you from financial damages that might come as a result of physical ones.
If at all your premium decreases it could be because your IDV has reduced. Or perhaps, you had a claim-free year so you can ask for NCB discount. Or perhaps you chose to discontinue certain add-on covers. For example, you may have had a zero-depreciation add-on but that would be valid only till the 5th year. From the 6th year onwards, since the add-on is discontinued, your premium is lowered by default.