For me it's a lot of reasons.
It wouldn't be a true sims sandbox with other people potentially interacting with my house, my characters. Because of other people, I wouldn't have a full range of actions likely either. TS4 more than proves this by it being meant to be online, scrapped, and now offline but missing so much game play and actions from previous sims games. To be fair though, I wouldn't want a full range of actions if it were online either. How creepy would the entire romance menu be with complete strangers? Predators would come from all over to play this. Ew, just ew. Never mind the mischievous or mean options either. People just randomly coming up and face slapping a sim? Funny for the first time, annoying for life after. They could leave all of this out though.
An online/offline version? Offline would still suffer with less options. Look at TS4. What about expansions? Guess online couldn't have those because how would people see each other's content? Or interaction with a skill item that only came with said pack? Bye bye modders and CC creators. They would likely handle this with a subscription fee. Pay monthly and everyone gets all the content, whether you want it or not. No more choices on your game customization. I also imagine this would be overpriced. I would be right ticked off if I were paying the price of a stuff pack every month just to get a hot tub... but, they do need money to keep those servers running. (Which would likely be broken more than their up if other EA games are any indication how that would be managed, more on that later).
Private servers or games then? Yeah... That MIGHT work, but if you follow EA Help on twitter and see that most games their servers are down and broken dang near every weekend, I have zero trust that they could get it to work for the sims. I have no desire to be like the Fifa and Battlefield fans who can't play their games during peak times, when people have time off to actually want to play their game that they've paid for.
Basically I see it as being a more broken and watered down version of what we already have. Looking at past and present games across EA I've got every reason to be worried. I'm looking for a more in depth version of this game next and this would not be it. It would have more limitations that this version, but, to be fair, it would have to be to protect the public and children that play these games.
They tried online in the past with sims online... dumpster fire. Tried again with simport in TS3, another dumpster fire. Ok fine, Simcity online only... the biggest dumpster fire of them all. They've tried this THREE times already and every time was a disaster. It boggles my mind why they are so keen to crash and burn yet again.
I like coming to the forums or even twitter and interacting with other simmers and talking about the game and showing off screenshots. I don't want you guys or anyone in my game. That's MY place to build and tell stories and I don't want someone else just changing the story board, (so to speak).
Oh yeah, stories. That would be a harder thing to do with sims online. You can't control everyone. Probably could say goodbye to a lot of that too. :/
