Why duplicating styles for Button in hybrid template?

[Binetri]

Ted, thanks for your hard work. It is really very difficult to make up HTML for e-mail for different clients. I want to understand a little more than just copy and paste :) Explain, please, for what purpose to duplicate styles border-radius: 4px; background: #222222; for <td> and for <a> tags on these lines?

https://github.com/TedGoas/Cerberus/blob/a2318a28a598cef4d86ef0a30c160431fe49b462/cerberus-hybrid.html#L285-L287

And duplicate classes for :hover events:

https://github.com/TedGoas/Cerberus/blob/a2318a28a598cef4d86ef0a30c160431fe49b462/cerberus-hybrid.html#L163-L168