There were several great companies building horns at that time.
So the idea sprang up that what was needed was a great playing, pro feeling and sounding horn which could stand more abuse, more wear. The companies didn't want to build a 'student horn', so as to tarnish their venerable reputations. The big bands and the jazz ensembles acts were everywhere at the time. The idea of a student trumpet came about during the late forties and early fifties when trumpet sales were heating up.
First of all, I would like to clarify the term 'student trumpet' so as to not to confuse the history buffs.