First, I know a lot of the "new" evergreen keywords got introduced in FST, but Fight wasn't one of them. We got that in ISD thanks to the gorgeously simple design of Prey Upon. So Fight wasn't around to be written on this.
Second, Fight is explicitly defined in the rules as between two creatures only. I suspect at least one, if not both, of the playerbase and the underlying MtG mechanics would deal badly with the issues of multi-target fight. (E.g., since this isn't combat, how is damage assigned across multiple creatures and who decides it?)
(Research later: Tabak says the underlying mechanics could handle it, if they wrote the rules for it, but they've chosen not to do so because it leads to unclear outcomes).
It's also worth remembering that even the Polukranos/Master version has weird issues, which people tend to gloss over because the flavour makes it work, but are actually confusing if you really think about it without a decent grasp of the rules. They led to quite a few questions for casual players, and I think multi-target Fight would do the same thing.
Unlike Fight, it's not technically simultaneous damage. While state-based actions aren't checked in the middle of a spell resolving, and therefore your Wolves get hit back even if they kill something first, stuff that isn't state-based still goes off. If you've given your Wolves Wither, for example, those -1/-1 counters go on the enemy creature first and reduce its power accordingly for the crackback. That doesn't happen with Fight which is truly simultaneous, but when you create multi-target Fight, you will make people who aren't fully au fait with the fine print start asking if any particular one is dealt damage or dies before any other, and stuff like that.
I can see it possibly happening in future, but they haven't done it yet for good reasons.