The "Why?" section on this site says things like 'it runs fast, can be customized to match branding, has a small filesize' etc.. But I'd like to know "Why?" as in "Why even add this supposed eye-candy to a web page in the first place?" I assume the answer is that it makes the page seem luxurious and opulent, which translates into the viewer believing that the page was probably time-consuming (and possibly expensive) to build, which translates into a sense of legitimacy and trustworthiness.

That explanation might have made more sense a decade ago before these types of effects were ubiquitous on the web. Now, it's easier than ever for anyone to drag and drop one of these preset visual effects onto their webpage. There's nothing to it anymore, people have seen them, the shine has worn off: There's no longer anything 'special' about these special effects.

Worse (as another commenter posted about always seeing these effects on 'crypto coin' sites) these effects are often used on sites engaging in confidence tricks - relying on dazzling the viewer with visual effects to convince them that their fraudulent scheme is legitimate. I associate stuff like this [0] with 'scam'

[0] https://img.freepik.com/free-photo/gradient-dark-blue-futuri...