Apostrophe rules can get complicated when we refer to possession by plurals or possession by entities with names that end in "s". Example: "These are our drivers' cars." Note the position of the apostrophe in the plural case. It's hanging out there by itself. But we also have instances like "This is Elias' car." This was the accepted way of indicating possessives with names ending in "s" for many years, but more recently, it's become acceptable to double up the "s" as in "This is Elias's car." The reason why the latter usage has won out is because it's spelled the way we typically pronounce a sentence like this. We say /eliases/ [ə'laiəsəs], not /elias/. So we're pronouncing that second "s". But it didn't always used to be this way. I can recall when I was in grade school that the teachers were quite strict about only the single "s" being pronounced in possessive instances with names that end in "s". Even back then, the second "s" was pronounced in common vernacular, so I always regarded it as a stupid rule. And I guess enough others did too, such that the language prescriptionists (grammarians, who do make the rules and who do judge) finally relented and gave way.
The lack of standardization with stuff like this caused me a lot of grief in school. In elementary school, I was taught that the possessive form of a word ending in "s" always had an apostrophe at the end without an additional "s" (eg. Chris', families', mass'). Then middle school came around and suddenly that was incorrect and would negatively affect your grade, because if the second "s" is pronounced when speaking, it should be written (eg. Chris's, families', mass's). Once I got to high school, I was taught that if the word was plural, one should use only an apostrophe. If the word was singular, use an apostrophe and s (eg. Chris's, families', mass's). Now that I'm in college, I try to follow the AP style guide, which of course makes things extra complicated by including rules for things like words ending in "s" where the "s" is silent, or instances where the possessive word is followed by a word beginning with "s."
Apostrophes are also often used, albeit incorrectly, to clarify because it is felt to be needed. E.g., "one's and two's and three's" when it is perfectly acceptable and correct to write "ones and twos and threes". Another example, a bit closer to home. "I own two 50mm f/1.2s" is often written as "I have two 50mm f/1.2's". People feel the need to use an apostrophe after a numeral if it is a plural term, when this is clearly wrong grammatically, since the apostrophe never indicates 'plural'.
Unnecessarily adding apostrophes to numbers frustrates me, too. I get annoyed whenever I see decades written with an apostrophe before the "s" - eg. 1990's or 90's rather than 1990s or '90s.