Two is correct formal usage. This started changing about 15 years ago... There is an evolution to one (this is often justified with texting, etc...). You can generally assume that people who "know" that single space is correct are under 40 years old.
That would explain it. I was taught two-spaces when I learned to type, decades ago. Since then I've gradually had to try and stop doing it 'cos people (and word processors) keep insisting its one-space now (but I can't seem to give up the habit). I have wondered if it has anything to do with the type of font one is using? Is it two spaces for something like courier, but one for proportional fonts, maybe? Anyway, I'm sticking with two, too old to change now.
Besides, the internet is full of people who use no white space at all of any kind and post walls of text with no paragraph breaks, so if some of us didn't use too much space to compensate there would be a cosmic imbalance.