It's not about upping game really. And it's not the longest by much if it's the longest at all. We just got spoiled because through much of iOS 8 Apple didn't bother patching exploits so we got spoiled to iOS releases followed a day or two later by a jailbreak. THAT was abnormal. This is not. There's a few things one has to remember even though some of it is uncomfortable/unhappy to those of us who love/use jailbreaks:
The number of people who jailbreak compared to the number of people who use iOS is incredibly small. Not significant at all. It's always been that way however this affects a few other things...
Apple cares about security (now much more than through iOS 8), because the vast, vast majority of it's users care about security. They prefer frequent patches that plug any holes that come up. The frequent updates are not so much a "let's fuck with people who want a jailbreak" as a "this is a serious security risk so we need to fix it". Jailbreaks by their very nature require a phone to be un-secure and it's certainly not the safest thing to do. A byproduct of Apple sharing customer concerns about security is that anytime a hint of a security issue pops up, it gets fixed ASAP.
Jailbreaks also increasingly become less and less worthwhile. As iOS offers more and more stock that used to be done via jailbreak, there's less and less demand or need, and it's becoming less worthwhile for developers to work on.
The community. It's toxic. Even for people who provide jailbreaks or tweaks, it's toxic. It puts developers and potential developers off. If you do one thing for the community, they'll expect you to slave for them forever and will literally bite your head off if you disappoint them in the slightest way. Chinese developers for example. Remember when they started? Everyone was bitching and pissed that the evad3rs and other western developers were not releasing anything. Chinese come along, INSTANTLY through the entire community they're mocked and insulted. "This is shady shit because it comes from commie China, fuck those people where are the western teams? These guys are out to hack our shit and steal our bank info." That kind of shit and worse. However when the next version of iOS came out, people were then lit that the Chinese developers were taking so long. They went from getting shit for being Chinese to getting shit for not immediately dropping everything and slaving for a thankless community that had just been extremely racist to them without any kind of valid reason.
There's a lot of reasons a jailbreak hasn't come yet. It's impossible to pinpoint a single reason. It'll come, but they're going to get less and less frequent. It sucks, but it is what it is. The community needs to change a lot if this is going to change.