Who's to say I'm not the one making the hashtable? There are plenty of real-world reasons the standard library hashtable may be either inaccessible or unsuitable.
Furthermore, the idea that "oh, honey, it's too hard, smart people did it for you" is insufferable and needs to die. When I'm the one making something, I have dramatically more information about the problem I'm trying to solve than the author of a hashtable library, and am therefore much better equipped to make design decision tradeoffs.
Please stop perpetuating the idea that 'just use a library' is unilaterally the best option. Sometimes, it's not.