“No smartphone” is a boundary, and U.S. parents are often raised not to set boundaries under threat of mental, emotional, and/or physical abuse. So it makes perfect sense that we have now-parents completely unable to define and discuss boundaries with their children. Far better to capitulate in the face of an uncertain and not life-threatening risk than to allow their child to ever think that boundaries are healthy, etc. For the unfamiliar, here is a good starting point for understanding the generational cognitive dissonance in play: https://www.issendai.com/psychology/estrangement/contradicto...
It's starting to change in places, including in the US.
The reality is it's not the smartphone, but the slot machine type software running on it.
There's more than enough science that placing this kind of content in front of humans before their prefrontal cortex is fully formed at age 25-26 leads them to leaning on the pre-frontal context of the adults around them, and missing that, whatever they're spending the most time with that's then possibly raising them.
Screens at lower resolutions and quality didn't seem to be as much of an issue compared to the hyper saturated motion with sound effects that are consciously chosen to keep eyeballs.
Like anything, digital can be used for good, or bad, and in lieu of good, the other can to happen and become more of a default.
Even the most Laissez-faire of parenting has boundaries; no reasonable adult is allowing their teenager to experiment with heroin or giving their 12 year old permission to drive their car down the freeway. The problem is that smartphone access isn't seen in the same category of danger that recreational opiates and unlicensed driving are in.