In the United States, at least, the norm is that you send official transcripts once you are offered the job. At my university (and I believe by SACS regulation) the transcript(s)/degree(s) must be on file with the university for all faculty members, thus it is a requirement to be able to get the job.
During the application process, though, unofficial transcripts are generally sufficient, if they even ask for it. Sending official transcripts to 100 different places in the application process would get very expensive, very quickly. For example, if they wanted from every post-secondary school I had attended, I would need to request transcripts from no less than 8 different universities, some of which would just have a course or two I took in summer programs abroad or were unrelated to my field. Even if they only needed my terminal degree, at $10/transcript, it adds up fast in addition to being a gigantic hassle for everyone involved.