The benefit would be that for a long time it was the only option in NeoLemmix mechanics - the option to disable it was (reluctantly) added in, IIRC, V1.35n-B; and enabling it is still the default, the option is not even present in the quick pack properties editor in the Flexi Toolkit, but only in the more-detailed SYSTEM.DAT editor in the NeoLemmix Editor. There are levels out there that rely on this behaviour, some of which could not easily be adjusted to not rely on it - especially if the creator wishes to stay within the "traditional" options (those not so worried about this could often solve it via the use of updrafts). Therefore, the benefit is reducing the number of existing mechanics that are being changed. And as mentioned before - there is even an entire graphic set (the Sky set) that is designed around the assumption that such a mechanic exists; certianly not to the point it won't function otherwise, but to the point where the exit is clearly designed to be placed in mid-air rather than on terrain. And yes, multiple levels using this set rely on a direct drop. (One possible answer to this is to allow two different types of exit objects - one that allows direct drop, one that does not. This is arguably an even worse solution than having a pack-wide option.)
The option was, for the most part, added because one content creator was so adamant about not wanting it, that rather than allow it (or design their levels to prevent it), their preference was to modify the source to create a customized version of NeoLemmix that does not allow it. Given that someone was willing to go to such lengths - which would also potentially cause hassle during development of their pack, not to mention needing to re-modify the source code if they wished to update to a newer engine version - I relented and quietly snuck in the option to disable it, to save them the hassle (you might notice that the changelogs, to both the player and the editor, make no mention of this option being added). Had it not been for this, the question would not even be on the table.
I do agree that having an option is less favorable than having it fixed to one setting or the other. In this regard, yes - more people say "always disable" than "always enable", but the majority opinion of all is "make it creator's choice". Yes, this does introduce an inconsistency, but I would also think it clearly indicates that there are people who want to be able to use this mechanic in their levels.
Perhaps another angle we should look at - is there a good way to solve this problem, without forcing those who want to use this mechanic not to, and without introducing an inconsistency? The two-types-of-exit approach mentioned above is one such method, but as I mentioned, not a very good one. If an alternative way to handle this comes up, then that reduces the need to have it as an option. (One possibility, perhaps - since overlapping trigger areas should be much less problematic in NX2 than they currently are - is extending the "floaters and gliders can exit" to include "fallers passing through an updraft can exit" as well. However, this does come back to that it makes the approach much more obvious in levels that do use it, than a pack-global option or consistent allow-it behaviour would.)
I've put up yet another poll - removing the "pack creator's choice" option, and instead asking which people would prefer if it had to be one or the other consistent behaviours. If there's a strong opinion in favor of don't allow it, then perhaps we'll say goodbye to direct drop - feel free to give input on what should happen regarding levels that rely on it. If it's mixed, or in favor of keep it, then it looks like giving pack creators an option is the only way forward - with a clear indication in the pack's information as to what the pack's setting is, I have not at any point considered keeping it "secret" that a pack allows it or not.
For the avoidance of doubt, this is NOT saying that I'm no longer considering making it an option; this is just in the hopes that asking what people would prefer if it had to be one or the other, might give a better indication of whether or not the option should be there. (Perhaps I should've divided the "make it an option" choice into two choices, depending on what the person themself would prefer to use...)
On a note unrelated to direct drop, but related to the initial subject of this topic - I think it's pretty clear that we are no longer going to have a "timed bombers" option. However, the physics do still need to allow for a countdown, for the radiation and slowfreeze objects to work properly. With that in mind - since the skill is instant, but it would not be difficult to have a timer in this case - should the Nuke continue to have a 5 second countdown? (Since any nuking is generally going to result in the end of the level, except in surviving-bombers levels (and in that case, it makes little difference whether it's timed or not; since you could just wait 5 seconds longer before hitting it), this is more or less a purely cosmetic question.)