It's not just features, it's a 350kb js file you have to send over the wire [1] as opposed to pre-building and sending a tiny css file containing the small subset of classes you used.
Not to mention, I don't know exactly how it works, but I assume it's doing all that processing to convert classes in your HTML into CSS classes on the client side so it's probably less performant.
[1] https://cdn.tailwindcss.com/
