Whether it's a bummer or not, the point is this is how every website has worked for the last 30 years.
I find that if you look closely at old books, the spacing is pretty variable. I have one book by my desk from 1895 and the spacing after a period is more like 2½ normal spaces, but I have another book from 1978 and the spacing after period is basically identical to the spacing after a word. There's not much consistency from book to book.
Yeah, it makes sense for HTML -- there is no easy way to differentiate sentence-ending periods from other periods. This is just one of those things that gets worse as technology improves. Another example is phone connections -- phone connections used to be fantastic, and they worked even when the electricity went out, but now we have cell phones, which commonly have terrible connections and are dependent on electricity. Just another example of how advancing technology degrades the user experience in order to achieve other efficiencies.
In general, technology makes things worse but cheaper. :-)
A book printed with letterpress is nicer than a laser printed book, and an illuminated manuscript is even nicer! There are some technology shifts where the new thing is strictly better, like DVD to Blu-Ray, but the majority of the time you have give something up to move forward, like losing the ability to record when we left VHS behind.
AI is going to really accelerate the trend by being really bad at a lot of tasks, but good enough to make do with.
I find that if you look closely at old books, the spacing is pretty variable. I have one book by my desk from 1895 and the spacing after a period is more like 2½ normal spaces, but I have another book from 1978 and the spacing after period is basically identical to the spacing after a word. There's not much consistency from book to book.