There is no good reason not to believe that Paul wrote Titus and 1&2 Timothy. Yet, some scholars, on the basis of the size and pagination of very early codices, conclude that the pastorals were not included in collections of Paul’s writings.
It seems that the production of books (codices) were commissioned by people or churches who had the means to have them constructed. In the following post, is an example of a book that contains various works such as Melito on the Passover, Jonah, and 1Peter. In the ancient period, all production of written material was manually performed. Collections of sacred texts were hand-produced, and thus, custom-made for their clients. It could be conceived that some books lacked Paul’s instructions to his proteges by Christians who wanted the scope of their books to not have these “personal epistles” included. However, Brent Nongbri has uncovered another reason to be cautious when using a codices’ pagination.The Pagination of the Crosby-Schøyen Codex and the Problem of the Contents of P46 — Variant Readings