Because those titles are very long and therefore hard to memorize by themselves, or easy to mispell/annoying to type out, and are commonly known by those abbreviations. Since Jojo is referred to by its Japanese name perhaps it would be good to also include something like /jjkb for jojo no kimya na bouken.

/haganai, the (arguably silly) official abbreviation for boku wa tomodachi ga sukunai, is already aliased - just in case you didn't know.

No opinion on the suggestions.

Bokotomo is only used by foreigners from what I can tell but I guess I'll add it. Get in the habit of using Haganai though.

Did jojo as well (it's jojo_no_kimyou_na_bouken)