When the web first became popular around the mid 1990s, many computer experts learned HTML, and they learned that different web browsers can make the same HTML look different. There were some efforts to spread the word that web pages should be about content, and that web designers should not try to exert much control over what the web page looks like. For instance, using an <H1> header tag may have different effects with different browsers.
I don't mean anything crazy, maybe a web font
You make it sound like "a web font" is a simple thing. Some people tried to use different fonts by having web pages download graphics that contained pictures of the letters. When support for fonts started to be supported by Internet Explorer, I recall there being significant challenges from common font files being unsupported by certain web browsers.
A lot of companies figured out that paying customers frequently liked pretty websites, and they could have such sites by getting "graphic designers" to be in charge of website design. Such people were often familiar with creating advertisement materials on other platforms, and so they were used to having lots of control over how things looked. They favored making websites that specified customized looks for everything, leaving very little room for a web browser to apply a different default setting than another web browser. Such control often involved loading more files, creating a slower web, and creating websites that really didn't work well on anything except for certain configurations, like computer screens that were over 12 inches tall and 800x600 (or larger, especially after typical technology improved over time).
When mobile devices, like phones, became far more popular, then suddenly a lot of professionally-created websites, created based on tons of assumptions, had problems. You might be surprised at just how many of these academics' websites kept working just fine, because their simplicity permitted lots of flexibility with browser rendering. Of course, the people were created atrociously beautiful websites had years of experience calling themselves professional web designers, so they actually benefited from the problems experienced by their creations, because they managed to have a built-in excuse for asking people for more money. After all, new web page designs were needed to accommodate mobile devices which have grown in popularity.
I, for one, appreciated the simplicity of having most websites use hyperlinks that are easily identifiable by having underlined blue text. You seem to have a differing opinion, and I'm not trying to pick a fight about the topic. (Such discussion may be more appropriate for the webmasters.stackexchange.com site.) I'm actually just trying to answer your question. To recap, my answer was: simplicity.
I would rather have websites that can be loaded quickly and rendered quickly, easily parsed by automated tools like web spyders, so I can just find the desired information and move on. Although one of my websites has some more functional CSS than what I've encountered on most sites, many "scrap" sites are hand-coded and use minimal formatting. When I do use formatting, I tend to use browser tags like <H1> and <STRONG> rather than trying to tinker with how the site will look with a specific browser. If you don't like how my site looks in your browser, then the most appropriate way for that issue to be fixed is for your browser to render things differently, not for me to waste a bunch of time trying to impose a specific look (which you happen to like, and which other people may not).