I can think of only BA who exclusively take integrated low hours, which is not direct entry.
Some people say because the students progress is well documented, each little section has a relevent test or exam and all come with a written report.
Some say that because the student does ALL the training at one place and in a short space of time that it is of a known quality.
Some say that because they have always taken their low hours from school a they will always take from school a. They have always taken from integrated they will continue to do so type of mentality.
Maybe they have some sort of affinity with a school/course type as they used to run their sponsored cadets through the same course. They had a good experience so they keep going back. After all if it aint broke don't fix it.
On the face of it im not totally sure why BA limit their low hours SSP cadets to integrated, Iv flown with some excellent mods and some not so good integrated but on the other hand I have seen some outstanding integrated and some poor mods.
Swings and roundabouts maybe?
Nick