Agree with this completely. My son (4) has SEN and frequently comes home quite discombobulated from nursery due to the overstimulating environment. He has 30 minds - 1 hour of TV time while I make dinner and it makes such a difference to his overall mood, he is so much calmer.
I don't think kids need hours on end of screen time, of course it is bad for them and often times is a lazy approach to parenting. But so much is not considered, and you have stated the reasons why parents do this perfectly.
Single and FT working parents don't always have the time or emotional resource to entertain their kids every spare minute they get. Yes, children can entertain themselves for a period, and they should. But its naive to think they don't come and seek attention every so often. It can be every few minutes. Is that their fault? No, they're kids, they need attention. Can parents give kids attention every few minutes that they require it? No, they're busy, they're exhausted, etc etc etc. It just isnt practical.
That being said, screen time should not be the only solution. But it is a great way to keep them distracted so you can have a bit of time to reset, or do what you need to. You shouldn't be forcing screens on them all the time, but doing it sometimes isn't a bad thing. The quality of what they are watching is crucial. I feel there is a balance that can work out really well for everyone with regards to screen time, when it is implemented properly.
The reality is that when parents get overwhelmed and LOs dont always want to entertain themselves, the parent may become agitated, even shouty etc. Is it better to be emotionally exhausted taking it out on your children, or to let them have some screen time so you can reset?
I think back to my own childhood. 2008 I had the TV, Nintendo DS, Nintendo Wii, PS2, and so on. Parents have relied more on screens throughout time than people would care to admit. The PC was on all day at my auntie's house in late 90s - early 2000s. I still played with toys, played outside a lot. As others have pointed out, parents don't feel safe to allow their kids to play out anymore, often times. Even if I felt there were no environmental safety risks, I certainly wouldn't be able to allow my son to play out alone with his friends due to his additional needs.
There are so many nuances and factors involved in this debate, that I really don't think its a one size fits all matter.
People saying how their kids have never held a screen, clearly casting judgement on those who's kids have. Its such a judgemental mindset and not one to wear like a badge of honour. If you've achieved this, that's great. Its not possible for everybody. With the exception of 'lazy' parenting, I think properly, mindfully controlled screen time can be a really useful tool for those with limited support, or those working full time.
Edit: didn't mean to reply to this quoted comment; was replying to the OP.