Well, others don't compartmentalize things so tightly.
Most would welcome one or more jokes in a developer speech. So much so, that it's common advice for any kind of public speaking and presentation to add a few jokes to lighten the mood (you can find thousands of articles, books, and public speaking training sessions advising about this).
Some of the best technical speakers add humor in their presentations (often lots of it, e.g. Raymond Hettinger).
Most would welcome one or more jokes in a developer speech. So much so, that it's common advice for any kind of public speaking and presentation to add a few jokes to lighten the mood (you can find thousands of articles, books, and public speaking training sessions advising about this).
Some of the best technical speakers add humor in their presentations (often lots of it, e.g. Raymond Hettinger).