Well, if they're as insidious as you say (and they probably are!), why should they stop when they clearly can get away with whatever it is they're doing?
Apple is the most profitable phone manufacturer by a vast margin. They literally eat everyone else's lunch except for Samsung, who gets to keep a starter course for all the efforts they put in. LG, Sony and just about everyone else pretty much subsidize their phone divisions with profits from elsewhere, or they did last time I checked anyway.
So skimping on RAM works, obviously. Not just from a profitability standpoint, but people also agree, since they're buying iphones in droves. And I agree as well, I used my iphone 5S up until when the 7 model launched last year and even with the current release of iOS it was very snappy and responsive, and didn't suffer from any noticeable slowdown or bad performance. My iphone 4 did, though. Upgrading it from 6 to 7 nearly killed it, even despite lacking almost all of the fancy-pants special graphics effects added in the new OS release. It was SO SLOW it frequently lagged even when keying in the unlock code, when the phone wasn't doing anything else at the time. Lots of lag elsewhere too in the device.
The 5S however wasn't like that, even though it only has 512MB (IIRC) RAM.