Keep in mind that in real life, unit tank trains like the ones Chris mentions are only used to haul fuels (such as ethanol or biodiesel, which are subject to water contamination even if shipped in dedicated pipelines) that cannot be shipped via pipeline from the refinery/etc. to distribution points, not to their final destination; tank trucks have been and will always be used for moving fuel or other similar products from distributors to fuel stations and other end users/customers for the reasons you've mentioned.

Trains are good at moving very large quantities of products and raw materials over long distances to factories or to warehouses and other distribution points; trucks are good at moving raw materials (if direct loading to the trains isn't possible) and products to the trains and products from trains or distribution points to their final destinations. Both modes of transport can actually complement (rather than compete with) each other, and that's why intermodal transport is becoming (or has become) the preferred approach to hauling most products, rather than using just one mode or the other.