> some freight trains are just too long to pull over onto a siding.

Exactly, and in addition to the blocking passenger trains they're at greater risk of derailment [1] and in some communities, particularly rural poor communities with little political power, they block crossings for as much as 30 minutes at a time [2] blocking ambulances, preventing children from getting to school, etc.

[1] https://www.propublica.org/article/train-derailment-long-tra...

[2] https://www.msn.com/en-us/news/us/stalled-freight-trains-cau...