Ok, this is our second favorite question!
The short answer is because we have short attention spans.
We want your audience to hear everything you have to say. Studies show that 75% of viewers will watch a 1-2 minute video all the way through. {source: https://wistia.com/learn/marketing/does-length-matter-it-does-for-video-2k12-edition} So we made sure your personal brand videos fall in the attention span sweet spot!