Because it would allow leeching and selling floors like mainscape.
lol, barely anyone even does this on mainscape. there's only a tiny [like, literally a dozen or less people,] amount of mains capable of efficiently doing solo larges with 4 leeches, who are part of that 'dungeoneering speed running community' [there's even a spreadsheet of people doing it,] and i can make a safe assumption to you that none of those dudes have a maxed ironman or an ironman with 120 dungeoneering with optimal bindings to sell floors.
people barely / hardly even sell token farming, and it's pretty much the best method of doing dungeoneering until ~99 - 105. most token farming is interclan with other ironmen helping other ironmen in the community.
this is literally just a fabricated issue that has no logical basis behind it like a majority of the stupid shit on this subreddit, and the further you actually think critically about it / introspect about it, the more it falls apart.