There's nothing stopping people from decorating their boutique stores (or personal blogs, portfolios, and fan websites) the way they want. And that's fun and delightful for me, as a visitor, just like boutique shops are IRL.

But I really don't need that quirkiness at Home Depot, the DMV or my bank (or Amazon, or government websites, or my banking site). I'm there to purchase some screws, register my car or pick up some checks. I just need a storefront (or a website) that lets me do that as fast and homogenously as possible.

99.9% of stores (and UIs) are the latter, not the former.