Whom are you referring to: SLOW?
Two is traditional, that's what I learned way back before teh interwebz, but one seems to be "the new black", at least according to Millenials. A far more important question is, why can't they capitalize the first letter of each sentence? Does it really take THAT much more effort?
two spaces result in greater paper consumption. hence two spaces mean you hate the environment, trees in particular, planet earth and all its inhabitants, in general. you don't believe in global warming and think jesus will return triumphantly to jerusalem with an army of angels to kill all the non-believers.
one space. We just had this discussion maybe a month ago. Two spaces after a period have been gone from professional publishing for decades. No longer needed and i doubt you will find a style book anywhere advocating for two spaces. Controversy resolved.
So new york vs. Chicago style pizza...
Only slacker college kids trying to make the 10 page minimum use 2 spaces.:x