> In general I'm not a big fan of unit test on simple websites, they do not give any real value compared to effort

And then your site gets more traction, features are added, things are refactored.

And now you're looking at what used to be a simple site, still with no tests.

It's a habit, that pays off long term. You don't do it for yourself, you do it for who changes the code next. Might be you, or not. Even when you do it yourself, you can't hold all the requirements in you brain, you write those up in tests