They know another attack is coming? The don't want to be harrased by racists? Hard to say. Schools make bank off foreign students tripple tuition.
Oh and this:
Saudi Arabia cuts funding for students abroad - Feb. 9, 2016
Thousands of Saudis may be forced to abandon their dream of studying overseas because of the oil price crash.
With its budget under enormous pressure, Saudi Arabia is having to cut back the generous scholarship program that supported 200,000 students abroad in 2015.
The government has been forced to tighten the rules of the $6 billion King Abdullah Scholarship Fund, limiting it to those attending one of the top 100 universities globally, or studying a program rated in the top 50 in its field.