I hate my cowplants! Please change my mind...

I don't use them all that much either. I usually toss them in household inventory after their use in the botanist aspiration. I would probably keep them out if they weren't so high maintenance .. but I'd rather not be tied to taking care of them everyday.
I do like the thought of using them for the essence(s) in gameplay but I play with aging off and I don't need the mood potions I can get from them as I know what objects or activities to do to get my sims in whatever mood I want them in. It's a lot of work and set up to get an unsuspecting sim to take the cake.
Mostly they are a lot of work for what you get.
That said they are iconic to the Sims... I wouldn't want them removed. To me they are on par with something like burglars. If we ever get them in game I'll be happy.. thrilled even. I'll let them break in a few times and enjoy whatever the devs build in around that event. Then I'll put out an alarm and forget about it until I want to tell a story that includes them. That's what I do with cowplants.