They know 14* Jinga is strong. They will not just hand a strong pet to you. Like you said, it's the "best pet" for Summoner, don't expect it to appear in your hands so easily. They will have CFs for it eventually, whether you believe it or not. Even then you don't need any of it. Farm for it if you want, but it's literally not essential, just like how Rykros Staff is not essential. I still do more consistent AOE damage with a 13* Jinga than any other pet, 14* or not. The drop rate is fine as it is.
Summoner gearing is so lenient compared to other classes. The playstyle is so easy compared to other classes. It's power is so tied to just the rarity of the pets, their levels, and candies. It's basically the same as asking for a 15* weapon to have a good drop rate if they were to be dropped. Well, 15s don't drop as often as a 14 Jinga does, so that's already great.