What if their name is "Bobs"? You'd have no way to distinguish the name as names are always going to be the least consistent part of the language - would you then use "Bobss"? But what if their name is "Bobss"…? ;-)
Funnily enough, if their name was Bobs then the possessive would be Bobs', but you'll see natives use Bobs's and even say "Bobses" (Gollum like) as it's confusing even for us. That kind of consistency isn't a strength of the language, and the education system is failing too many people (that's a whole other discussion).
> Funnily enough, if their name was Bobs then the possessive would be Bobs’
Actually, no; s’ is for possessives of plural nouns ending in s (well, an s or z sound, which might be an s, x, or z, but usually for a plural will be an s, and most plurals ending with s won't have it silent, but...); plural nouns not ending in s or singular nouns, including those ending in s, get ’s.
Except for the special rules for classical and Biblical names, where then the number of syllables in the base name (which then makes the s or z sound rule more interesting, because names ending with silent s, x, or z are a thing) becomes relevant because English.
I looked into this exact topic a few months ago when a cake decorator friend wanted to know what to write on the cake board for "name's christening" but the child's name ended in S. I applaud the attention to detail :)
Many style guides recommend the "Bobs's" form over "Bobs'".
Those style guides also mention many more special cases, like "the students' questions" (but "the dutchess's hat", because students is plural and dutchess is singular) and even break that down to the case where the next word starts with s, like "the dutchess' style".
Funnily enough, if their name was Bobs then the possessive would be Bobs', but you'll see natives use Bobs's and even say "Bobses" (Gollum like) as it's confusing even for us. That kind of consistency isn't a strength of the language, and the education system is failing too many people (that's a whole other discussion).