Output static HTML for the simplest websites.
Output templates in any language for the most complex websites.
For simple websites, you can:
Reuse components, like headers and footers, across multiple pages.
View a live rendering of the changes to your code as you make them.
Add more tools via extensions if your website grows in complexity.
For complex websites, you can:
Separate your frontend concerns from your backend concerns.
Maintain a styleguide and/or pattern library for permanent reference.
Easily version-control said styleguide or pattern library.
Retain control and flexibility:
You will not be forced into marriage with any CSS preprocessor, CSS selector paradigm, or holy war.
Life is already expensive. Why make it more expensive?
While costly subscriptions to paid online services may appeal to some, and code may frighten the same, there are no guarantees about the future survival of those businesses, or even the imminent uptime of their services.
Fepper is Open Source Software. It is free to put on your machine, and free to keep on your machine, forever.
A purely frontend website can be served from any host (including free ones), without requiring a database or preprocessing backend.