Even if the punchline is funny, it will stop being funny after you've seen it two or thee or four, etc. times. Whereas if a commercial is about motivating people for example, you can see that a lot more times before it gets old. TBH something like the Super Bowl would have been perfect for a "funny" commercial because you only show it once. Now advertisers are doing it for every other commercial it seems

Also a commercial like this is perfect. They weren't trying to be funny but it still is...

https://www.youtube.com/watch?v=4rqZZgVxnCk