1. Haruhi is based on light novels, so has to actually perform to get a release. Japanese market is upside down, the anime often goes to free to air to support a manga release where the real money is made (I have no idea how this works economically this is just how its explained to me) as there isn't any more manga or light novels to release, the likelihood of another season is low. It was sort of always a passion project.
2. The studio was firebombed. https://en.wikipedia.org/wiki/Kyoto_Animation_arson_attack
3. Season 2 was critically panned, but I dunno I thought it was pretty genius.
My suggestion, watch both series, then read the english translation of the novels.
Also don't forget to watch Disappearance after the 2 seasons.
The IP is likely doa anyway as it's on indefinite hiatus
I don't know how anime series economics works these days -- AIUI traditionally the live late night TV broadcast was effectively an advert to get the hardcore fans to buy the extremely expensive Japanese market DVD/bluray sets, which were what brought in the money. But I expect streaming has changed things a lot.
I'd assume streaming services have changed the industry. Things like Devilman Crybaby wouldn't have been released if Netflix wasn't involved.