Depends who you ask. To manufacturers it's a brilliant idea. It's not a mystery that no electrical engineer knows that Li-Ion batteries don't like to be fully charged. It's just that manufacturers realized that charging 100% means you battery will die at around 2 year mark or 600-1000 charge cycles and that will be enough push for some people to buy a new device while at the same time your device seems to last longer on a single charge. Charging to 80% or 85% significantly extends life span of a battery. At that point chemistry almost doesn't degrade.
And it's not just with mobile devices and batteries that this is happening. Engineering with a plan to fail at specific time has become a precise science. Making something that will last forever is not that difficult, just not lucrative to them. Take for example LED lights. Manufacturer states 50k hours at 3.1V for white LED. Reduce that voltage down to 2.5V and you have basically made it infinite but it glows less, so to compensate you'd have to add more LEDs and that hits their income. Big Clive has a great video on the subject.