No, video assets are not strictly mandatory for launching a Performance Max (PMax) campaign, but they are highly, highly recommended and contribute significantly to your campaign's reach and performance.
Here's what happens if you don't upload one:
Why You Should Upload Your Own Videos:
Maximize Reach & Placements: Videos allow your PMax campaign to serve ads on YouTube (including YouTube Shorts if you have vertical videos), and potentially more aggressively on the Google Display Network and Discover feed. Without video, you miss out on a significant portion of Google's inventory.
Control Over Branding & Messaging: Auto-generated videos often lack the polish, specific messaging, brand voice, and strong calls-to-action that a custom-made video can provide. You have much more control over how your brand is presented.
Better Performance: Google's own recommendations emphasize that including your own high-quality videos (ideally in various aspect ratios like horizontal, square, and vertical) can lead to better campaign performance and more conversions.
Ad Strength: Providing a diverse set of high-quality assets, including videos, helps improve your "Ad Strength" score, which is a key indicator of how well your asset group is set up to perform.