I think what is being missed here is the question of how much merely pointing out spelling errors will actually help a child to improve.
I know that, when I was at primary school, every error was pointed out and we had to write out the mis-spelled words. I am not, however, convinced that it made any difference at all. Is that a good way to learn?
We are time strapped and the children don't have the time to go over each and every spelling error. We need efficiency in all things so we need to ensure that everything we do drives the learning forwards.
Writing out the 12 spelling mistakes made in a piece of work achieves what, exactly? How does it help the child to improve?
It takes a lot of time and is only superficially solving the issue.
Picking out one important keyword and allowing the child to spend time focusing on that one word is better use of time than quickly writing out all 12 mistakes - so that is how I have (historically) marked upper KS2 children's work.
Lower down in KS1, the idea is to emphasise phonics and the learning of high frequency and common exception words and I don't know of a single primary school class where huge amounts of time aren't spent on those basics every single day.
We have a crazy language and learning to spell is actually really difficult.
Spelling in primary schools is a massive deal and we spend a LOT of time on spelling and grammar.
I don't know so much about secondary school marking policies.
The other thing I would emphasise when it comes to spelling is the importance of reading.
For me, the single most important thing a parent can do to help their child is to read and encourage reading. So much of spelling is recognising when I word 'looks wrong' and that only comes with wide exposure to the written word.
I don't know what the answer is, but I do believe that teachers are doing their best with the time they have.
I'm not in mainstream anymore, although I am still teaching and my challenges are slightly different in that my children are deaf and don't have the same access to phonics for spelling, so we have to use different techniques. Spelling tests, though, are largely ineffective.