95% of the information on the web is written language. It is only logical to say that a web designer should get good training in the main discipline of shaping written information, in other words: Typography.
Building structure requires serious listening, serious reflection, and serious imagination. All this requires experience, and no matter how experienced you are, it costs you. We spend our time and nerves to save users their time and nerves. Well-designed things give us the invaluable present of time. Well-designed products do not just save us time, they make us enjoy the time we spend with them. They make us feel that someone has been thinking about us, that a nice person took care of the little things for us. This is mainly why we perceive well-designed things as more beautiful the longer we use them, and the more used they become.
The far more pernicious issue with pangrams, as a means for evaluating typefaces, is how poorly they portray what text actually looks like. Every language has a natural distribution of letters, from most to least common, English famously beginning with the E that accounts for one eighth of what we read, and ending with the Z that appears just once every 1,111 letters. Letter frequencies differ by language and by era — the J is ten times more popular in Dutch than English; biblical English unduly favors the H thanks to archaisms like thou and sayeth — but no language behaves the way pangrams do, with their forced distribution of exotics. Seven of the most visually awkward letters, the W, Y, V, K, X, J, and Z, are among the nine rarest in English, but pangrams force them into every sentence, guaranteeing that every paragraph will be riddled with holes. A typeface designer certainly can’t avoid accounting for these unruly characters, but there’s no reason that they should be disproportionately represented when evaluating how a typeface will perform.