Energy security, not propping up authoritarian regimes with terrible human rights records, not requiring military interventions to protect a stable supply of oil.
Maybe not good enough reasons to change the balance, but reasons nonetheless.
Obviously, you're right long-term but it's a slow transition not a switch we can flip.
The problem there is if you need to do it quickly: if the SUV/truck trend hadn’t caught on, for example, fleet economy wouldn’t have reversed the improvements we saw in the 80s and early 90s. The longer we wait, the harder that gradual transition will be.
And trains lend themselves much better to slow declining transition than a new pipeline. Can be used for other cargo; are a bit more expensive so they are a mild financial disincentive; the contaminated material (tanker cars) are by definition mobile and therefore easier to deal with at EOL.