A while back there was a study published about having two spaces between sentences. The upshot of the study was two spaces after a period made reading easier, two spaces after a comma made things harder. There was, of course, controversy – which I won’t get into. I grew up and learned to type (on a typewriter) using two spaces before the next sentence. That is a really hard habit to break. It’s still not broken, by the way. I have to rely on settings in my word processor to ignore that second – frowned-upon – space. Finding that preference took me a while, but once found was very handy. Sure, I could finish the document and “find” the two spaces, then “replace” with a single space, but it’s far more convenient to have it taken care of ahead of time so I don’t have to remember to deal with it later. Sometimes things like that slip my mind, then I look like a total moron when I submit. Not that it’s a problem for publishers to take care of it, but getting past the gatekeepers is hard enough. No sense giving them another reason to reject. Personally, I like the extra space. There are reasons to omit it that makes sense to me. That second space might kick a word from one line down to the next, then another and another and another, and pretty soon you have to use an extra page (or ten) to print a book. More cost. If you’re doing a print run of a mass market book, that extra paper costs money. Books are already expensive enough, we don’t need to bump the price any higher. Still, I miss that second space. I’m pretty sure web sites are designed to ignore them, too. But I’ll try it anyway.
When I first heard I was "out of style," I searched through my personal library to see how many had only one space between sentences. I was going to prove everyone wrong. However, after a long search, I found only one book with two spaces and it was printed in the 1800s. A little studying taught me professional correspondence still uses two spaces much of the time, but not books. *sigh* So, for about a year, I worked very hard to type only one space between sentences. Once in a while, I still goof. (By the way, I saw your two-space gap.)
I, too, find the habit hard to break. I guess we are bowing to the 'easier on the pocketbook" mantra, and paying little heed to the 'easier on the reader' idea.