From what I have been reading lately, the use of bad grammar in speech is becoming acceptable. It is being called colloquial language. I call it an education failure.
should of – instead of should have
“her and myself” had lunch together – instead of “she and I”
could have “went” – instead of could have “gone”
There are many more, when you consider the written word as well as the spoken word
“your” – instead of “you’re” (contraction)
use of apostrophes in plural words
And there are more than I can count.