Harry Bloomfield wrote
Rod Speed wrote

I would say its only recently noticeable by some
as more communication is now by written word.

Yeah, I bet that is the main effect.

I wonder who used to see what the dregs wrote in the past ?

Presumably teachers and those who run the dole queues.

Actually, a very good point I had not considered - yes there is
much more written communication these days, but I don't recall
anyone who couldn't read or write to a standard before all of this.

I actually know a couple of them personally. And just last week,
I had a fellow who must be in his late 60s or 70s who does
occasionally show up in person to hand me a letter of mine
that has been delivered to his house in the next street over
with the same number as mine. This time it was one of those
letters that everyone gets, addressed to the householder.
He decided that there was no one by that name at his
place so it must have been one of mine gone astray again.

Yes, some of the stuff you see on the facebook buy sell swap
groups is stunningly illiterate and isn't just due to the electronic
keyboards that so many use for facebook now on their phones.
Like the very common use of the word draws when they mean
drawers and duel instead of dual.