I want to re-assure you that we take our responsibility very seriously. Payroll is a business critical task and we're committed to taking care of all payroll tax calculations, payments, compliance documents and filings for our customers. We have people on our team with 30+ years of experience in payroll compliance at ADP, Paychex and Intuit, and we've securely processed tens of millions of dollars in payroll. Our focus is on bringing the power of modern software to this industry and re-thinking the UX, workflows, automation, etc. while maintaining the security and stability you expect from a payroll product. If you have any questions or feedback, please feel free to send me a note at josh AT zenpayroll DOT com.

They aren't catering to stodgy, old businessmen with three chins. They are catering to a different audience and in that, they are succeeding.

Look at all the things they can communicate through use of a meme. Using the success kid meme implies that the customer would get a feeling of awesome accomplishment and it is applicable to the topic.

I am a little biased because I also use memes in my product blog posts for this reason. I suspect that they subconsciously do the same.