Because the taste buds are in the front of your tongue, not the back of your throat.
I assume you're joking, but for those who got taught that in school but haven't thought about it since, that thing is
basically bs:
https://en.wikipedia.org/wiki/Tongue_map
It’s a deep throating joke.
I know that part is, but specifically the front of your tongue tasting sweet is the weird tongue map thing that somehow made it into the education system