I've been wondering this myself. Northern's original explanation for the further reductions next month was to "prioritise" busier services, but there are no extra ones being scheduled elsewhere. The result of Bradford-Skipton/Ilkley going to hourly only save a couple of half-hourly peaks will be that at the busiest time of the year for the line, Bradford-Ilkley loses half of it's capacity (based on low ridership during the winter & covid restrictions), the commuters who would travel down the Airedale line on the Bradford services, changing at Shipley for a Leeds service a few minutes later will now just shoehorn onto the the direct services, and at Shipley now for much of the day there is a half-hour gap for services into Bradford. Plus we all know what will happen if there are delays or disruption, the Bradford FS services will be the first to be cancelled, meaning that for some passengers travelling to and from the city delays could quickly run into hours.
Its just going to further drive people back onto the roads, which is exactly what the roads along the Aire & Wharfe don't need. The local politicians who have been onto Northern have been told that the changes are "temporary", however based on Northern's current planning mechanisms they will doubtless justify further reductions in services by citing lower ridership following previous cutbacks...
Edit: And with almost comical timing, I've just seen an advert Northern have posted on social media about trains being able to take up to 500 cars off the road at a time!