The problem is that if trains are not run at a reduced speed, then some units may be out of service for some weeks/months. A few winters ago, almost every morning there were about 20 or so bulletins on SE's website of short formed services for a few months after the snow about short formed services because of the snow.
The choice is between causing disruptions for one day, to mitigate the risk of inconvenience for weeks, or having either more or less disruption on that day - it is impossible to tell - with potentially long lasting disruption.
I personally would rather be delayed one day and have a seat as usual for the next few months, rather than not be so severely disrupted but have to stand for months while the damage is fixed.
Just my spin on it
Joe