Giving them herbal medicine isn't "treating them like crap". There's bitter medicine IRL and sometimes you have to take it. There's no real way to treat Pokémon like crap in the game, except for maybe making them faint a lot, but you most certainly can't do to them what Team Rocket does for example (which is why Frustration is a pointless move).
It's not entirely treating them like crap, but it DOES make them very unhappy with you, and considering there's an option that doesn't decrease happiness...why use them? Combined with having them faint a bunch, it makes them hate you, and that goes against the whole point of the series, which is to befriend your Pokemon. Sure you can't kick them or kill them but that's because Game Freak thankfully never included the option to (and also you're the hero, why would you?) And Frustration isn't entirely pointless... it's just a visual representation of how horrible you are as a trainer. To be honest I don't get why they don't delve on it a little more, like having a Pokemon that hates you disobey you like a traded Pokemon would. Make the Pokemon is too afraid to disobey and just resents you deep down? Either way using bitter medicine is something I never do. Call me a bleeding heart but I can't stand the thought of the adorable little things hating me. :)
Even in RSE, some berries are better than others. Chances are you aren't wasting your berry fields with poison-curing berries when you could be planting Lum Berries there instead.
There's a disadvantage to using Lum Berries you forgot to mention: the fact that you have to water them precisely when they need water... to get exactly 2 berries a plant. They cure status effects, sure, but they're dang impractical to use because you have to farm enough of them for them to even be useful more than once or twice. You might as well just have a stock of each status berry because they're easier to farm than Lum berries and aren't nearly as hard to replenish. And also if you give them to a Pokemon and it's used up, that's it. If you were seeking to guard against a particular status effect like sleep or confusion too bad!
But even in GSC they weren't entirely useless. Those two Berries you got before you fought your rival for the first time was a godsend, and even if you could only get them once a day they were free and came in use if you didn't happen to have any Full Heals on hand. (And those Miracle berries man!)
Weeeelll.... it's not so much they lacked berries in FRLG... it's that they lacked replenishable ones. You could find berries buried in little holes in the ground. Once you got them, they were gone for good and didn't come back. The only way to get more was to either get a full team with Pickup or steal some off of Rattata, Jigglypuff and other Pokemon that would occasionally have them. Apparently the berry trees were in the endless woods your character couldn't go in but the Pokemon could.And FRLG didn't lack berries, either.