The problem to me about TS4 is the traits don't matter. The Sims' lives are so easy they don't need the player most of the time. Why would anyone want to make it any easier with sliders to set a difficult level.
The older games were smarter in ways than this game has been built. For instance, difficulty with Sims should always be based on their personality not a difficult level. But the older games had difficulty built into the game in specific areas such as getting a promotion and or retaining friends, and or retaining an intimate relationship. Those are simple ways to make the game harder or easier. In TS4 every thing is easy for the Sim.
In the older games, when skilling the first few points were easy like learning how to cook. Right? But as the Sim needed to learn more about cooking the level points became harder to gain and took much longer. That is the difficulty of the older games like TS2. And always the last few points to get to level ten in mechanical took much more time and harder to gain. This was good because Sims who didn't have a level ten mechanical skill could be killed if they attempted to repair the TV. More than not. It was a 50/50 chance at a lower level skill starting with level 5 etc. Anything below that the odds were your Sim is probably going to die. There was no Hand Holding. TS4 holds your hand and why many veteran players don't like it. That is just one example of no hand holding and the difficulty, but wait, money didn't just didn't flow into the Sims' lives like it does in TS4. The reason someone might want the Sim to have some better skills to repair their own stuff and or be a better cook is because what the Sim ate mattered and what the Sim could do with repairs mattered or the Sims would suffer low, very low motives and of course didn't have the money like in TS4. Things cost money, TS4 has more money that the Sim doesn't even have anything that expensive to spend it on. Such as clothes, cars, more expensive foods and ingredients etc.
TS4 is a simple, childish game that anyone can fly through because the only bad thing about the wrong foods in TS4 is it makes the Sim overweight. Well, in older games, it ends their life sooner, oh, yes, there is a meter that determines (hidden) how long your Sim will live when they age up to elder. Some Sims live longer than others. TS3 handled this better with better foods etc. And spoiled foods systems etc. And or better ingredients. What is the point of better food if it only gives your Sim a moodlet? (TS4).
Better foods in TS2 meant the sim wouldn't have to eat as soon and some of those foods will lower the Sim's fitness just not make them overweight. This also mattered depending on if other Sims preferred a fit Sim or not. It all mattered not just zodiac signs. Cooking skills mattered if the Sim was going to burn the food and the house down, now it just matters if your Sim can do some fancy cooking animations. So, no difficulty level slider was needed. You knew if they didn't improve (your choice play it easy or hard) they were going to fail, perhaps not be as attractive to the other Sim and or burn the food and the house down, because no, Sims don't auto put a fire in older games like they do in TS4.
There was a reason Sims needed a Fire Dept. and it's not because it's cute. It's because they are going to die and burn down half the kitchen and or more of the house if a fire fighter doesn't get there. No Sliders needed if common sense tells you the Sim needs some cooking skills at least one before they turn on the stove.
These are just small examples of how the older games handle difficulty levels. Money didn't just fly in the window such as being able to collect rocks all over the place and sell them if your Sim already has ten dozen crystals. There was reason Sims needed to find a job and fast. Because starvation, over exposure to weather, and or low energy and hygiene was going to kill them. Sounds reasonable doesn't it. I mean who can live on a bench (TS4) and be perfectly happy all the time (TS4) and never have to bathe (for over 24 hours in TS4) and or eat, and or pee and or talk to someone? Not many, at least not those with any self esteem.
TS4 Sims can live outdoors on a vacant lot and almost never need anything. Try that in older games and you will find out why TS4 is the baby of the crop and why we all know TS4 doesn't need sliders for easy -hard it needs a kick in the rear end and an old fashioned dose of reality.
It shouldn't be a breeze to be a Sim.
Before the BFF after Sims Studio took over in TS2 the Sim had to retain friends and it wasn't easy. The BFF was a way to make the game easy peasy for some. But once you got that you couldn't even break up friendships no matter what the Sim did...if you want easy just add BFF.
TS4 players are the reason TS4 is too easy for most of us. I just read where someone doesn't like they have to buy the embroidery loop to do the stitching in the Cottage Liv. pack....just have something in inventory..c'mon, I mean really..I have to shake my head. But you know, Maxis will probably hear that request and do it. :s I mean it's not like their Sim has to get off their duff and go to a store and buy one...omg, I had to click buymode and buy a one...sigh....