But probably (only my personal opinion here) , being it NOT a forum script, it was originally developed just for asocial-networks, and cause 90% of asocial-users are using smartphones (so-called "smombie" peoples 
), it was originally intended with only that use in mind, and the remaining 10% of users that use PCs can "shut up and joyfully go to hell" if they don't like it (as we say here 
).
So, there are 2 main errors, here ... first one is that the maintainers of this forum have choosen a script that is obviously NOT made for forums, without made a decent trial period of time before (and asking BEFORE to users what they think about it) ... and second one is from the developers of the script that distributed an asocial-network script saying that is good for forums, and don't care about develope a correct version for PC users (independently from the fact that this is done cause PC users are not the main interest, for lack of knowledge about forum scripts, or just from lazyness, this is not the main problem).
Also cause a lot of other places have 2 independent layouts, PC and mobile, that happily convives, so is not impossible to do, just they don't want to do it.
Just my humble opinion.