Why did Igor Stravinsky study composition privately with Nikolay Rimsky-Korsakov rather than attend a conservatory?

Igor Stravinsky did not attend a conservatory because, after he showed his early compositions to Nikolay Rimsky-Korsakov in 1902, the elder composer was sufficiently impressed to take Stravinsky on as a private pupil. During this mentorship, Rimsky-Korsakov specifically advised Stravinsky against enrolling in a conservatory for conventional academic training.1

Instead, Rimsky-Korsakov provided personalized instruction, focusing primarily on orchestration. He acted as a mentor by discussing each of Stravinsky's new works, offering guidance, and using his professional influence to help get his pupil's music performed.1