It Is Difficult to Get a Man to Understand Something When His Salary Depends Upon His Not Understanding It
It's hard to support a heterogeneous space of user agents running on a heterogeneous set of platforms. Eventually, abstractions break and you end up with a weird bug that only manifests on such-and-such browser in so-and-so configuration.
How much easier life is if you only have to support a few browsers on hardware that checksums to have a known-good configuration...
Chasing down render errors in the deep interactions between declarative HTML rendering and an esoteric-but-important hardware / software configuration is drudgework.
Some of my best ideas even, came out of clearing drudge.