The dates of Scottish school holidays are available on the internet.

There is still the uncertainty about whether or not the US border will be open for tourism and what requirements there may be when entering the US and then returning home. VS may have taken a view that it is better to cancel sooner rather than later especially if advanced bookings are low.
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When an airline cancelss a flight they usually notify people on the earliest flights first to offer them refunds or rebooking then move down the date list.

Also VS is only obligated to inform tjose that booked direct. If you booked using a TA then they should inform you and then deal with rebooking / refunds because they will be the ones doign that work.