Thanks to this parliamentary question from Scottish Labour, we can see how few trains have been ‘stop-skipping’ in recent times.
While ‘stop-skipping’ is hugely annoying for some passengers affected by it, there can be reasonable explanations for actions which are taken in the interest of the greater good of all the passengers on the system at any one time. See this:
Skip-stop is a public transit service pattern which reduces travel times and increases capacity by not having all vehicles make all designated stops along a route.
When skip stops are used in rail transit, the transit operator designates stations as either major or minor, typically by ridership. Usually, all vehicles stop at the major stations, but only some vehicles stop at the minor ones.
In systems that have no extra track for a faster train to pass a slower train, skip-stop may be employed either during busier travel hours to reduce travel time of a particular train, or during off-peak hours to raise efficiency by not stopping on “unpopular” stations.