Just want to point out that many of the best and most popular games ever made used BSP for level design, which in and of itself is an objectively good argument for considering including it. For example: every COD ever made (including fan fav COD4), every Quake game, every Doom game, every Half-Life game (including 3 yukyuk - but, seriously, Source 2 uses it), Portal 1 and 2, L4D1+2, TF2. Essentially every game somehow related to the idTech tree. I know not in the world likes all these games but it is undeniable that many of them have had an enormous impact on the industry, developers, even the world!
Arguing against supporting tools that use technology is quite silly.