Art historians from the Italian Renaissance did not consider artists who would attack a painting without due preparation as worthy of respect. Tintoretto was already an artist who did things his own way and was not concerned to do things differently. As early as his rejection by Titian, preventing him from commencing a Venetian apprenticeship, this was a strong character who would soldier on regardless of the obstacles placed in front of him.
The reality was that Tintoretto was a highly skilled draughtsman who understood and even loved this medium. He is now known to have produced study drawings for his paintings, despite popular belief. It is possible that his secretive nature meant that others simply did not understand him as an artist or as a person. It is only later that so many of his drawings have been discovered that a new opinion can be formed.
In all, there are several hundred drawings that have survived to the present day which can be confidently attributed to Tintoretto, or members of his small studio. This is a huge number compared to others from the Renaissance, mainly due to the fragility of this medium. Most artists also did not consider study sketches to be genuine artworks worthy of preservation at this time too. In many cases the drawings might be passed around a studio for others to learn and study.
It can be argued that Tintoretto himself was partly responsible for his earlier reputation as someone who did not complete study sketches for large commissions. He perhaps played into this view and enjoyed being considered impetuous, almost anti-establishment. The artist was also part of a wider belief that Venetian artists in general did not make quite the same efforts of preparation as compared to the Florentines. That belief can quickly be dispelled by studying the work in this page as well as some exceptional Titian drawings too.
Despite Tintoretto's early rejection by Titian, there are actually great similarities between many of their drawings. The unfashionable Venetian seemed to be battling against challenges throughout his life but still delivered a respected ouevre which has a greater inclusion of drawings now thanks to improved methods of research and attribution.