Let me say right away that I dont enjoy Eureka - however neither I nor the apparently huge amount of people who dislike the content speak for everyone, so I'd have to answers to your questions:
First of all there are people who like Eureka. Just because I dont like a piece of content, it doesnt mean no one does or that the content shouldnt exist - a lot of content is actually not enjoyed by the majority of people (crafting, raiding, PvP... yet all of them get updates). While playing a game should indeed be "fun", that can mean something different to every person - I dont find Eureka fun and I explained why in great length, so I wont repeat it here, but at the same time I can respect that someone else might find it fun - I know a few people who kinda like playing it excatly for the reason that its somewhat of a mindless grind they can do when they come home and are tired from work. Not my cup of tea, but it doesnt have to be. Doesnt has to be yours either.
Second - and probably more important: The devs most likely dont plan from patch to patch, but made their Eureka-concept during the development of Stormblood all the way through all 6 elements - at least to a certain amount of detail. They cant just pull the plug on it, just because Eureka wasnt well recived because that would mean throwing away all the work they did and replace it with... nothing. Some might argue that that would be better, but we all know that it wouldnt.
That they were planning and developing ahead is most likely also the reason why we saw so little of the feedback that was given in regards to Anemos inpact Pagos: They were to far ahead developing it to make use of that feedback - one can only hope that they're gonna make adjustments for the following ones now... even though I wont hold my breath on that.
...and maybe they're hoping that people will start to like it eventually...
By now I honestly believe that their biggest mistake in regards to Eureka was putting the relic in there - because now a lot of people who arent intrested in the content feel forced to do it (and they are, if they want the relic). If Eureka would have been truely as optional as crafting, gathering and UWU are, there would have been a lot less of an outcry.
Currently, people who just dont enjoy the content are doing it and are (rightfully) upset about the whole situation.