I can tell you the reason it is happening so much in Denmark. I don't know, but I suspect the reason is the same everywhere.
My generation of school-teachers - I started teaching in the 1970s - were taught to teach children to write by hand.
In Primary 1 you taught your class to hold a pencil usng their thumb and forefinger and letting the pencil rest on their middle finger during writing lessons. You started with letters i, o and u that could be written between two ruled lines in a jotter, and once the class had mastered these you progressed to all other letters that only take up the space between two ruled lines. Then letters like g with a tail that hangs down, and b and d that go above the top line. Jotters had thinner ruled lines above and below the ones the letters like a an u were on, so the tail of the g and the top of the f or l went down to the lower line and up to the upper as needed. I am sure you remember these jotters too.
Once the class had mastered the lower case letters, capitals were taught just as carefully and finally commas, full stops, colons, semi-colons, question marks and exclamation marks. And this took daily lessons throughout one or two years of school.
Marking written work, marks were awarded not only for the content. but for its appearance as well. Thus a child who was poor at spelling, might well be able to boast good marks for hand-writing and neatness.
We also taught children to sit up straight while writing (or reading) and only to rest their wrists (never their elbows - perish the thought!) on the desk. At this point, any child who persistently bent nearer to their work was sent to have their eyes tested! No-one would do this today either. And yes, we found the short-sighted and astigmatic and saved them many headaches due to poor sight.
Young teachers are no longer taught to teach writing - they just show the children how to form each letter and leave them to get on with it. They see no reason to correct the way a pencil is held, or to teach children to write legibly, as they will be using a computer or tablet most of the time and never need to write by hand. The children use any old writing pad or piece of paper that comes to hand with or without ruled lines, or even scrawl their way across a page of the small ruled squares we only used for sums.
Like me, you probably spent what felt like years at school making your upstrokes thin and your down strokes thick in "joined up writing". Thes days such a skill, if taught at all, is taught in art lessons in senior school for at most one or two lessons and called calligraphy.