I am working on doing my first website and I have been looking around at some other sites similar to what I want to do. I noticed that many of them are in .php. So I was wondering if they just decided to do this because it made them happy or is there a benefit?
Everyone used PHP because it was trendy. Be different. Be unique. Use Python.
If this is your first website though, you don't need to do dynamic content. Just start out creating static HTML files.
I think a lot of people use PHP because it has a small learning curve and can get the job done quickly if you know what you're doing. When I got into web designing, I started out with PHP as well.
If I did straight HTML how hard would it be to add fancy jscript with dynamic content and stuff later?
Really easy. All the dynamic code is normally embedded inside the HTML pages. So you can make a static page and add anything you want directly inside the page like javascript or php code.