It took me 3 years of about 2 hours a day in high school to learn approximately 6000 words in English, my native language. This was in addition to my schooling where I was writing essays and book reports pretty much weekly. Probably 10+ hours per week for history and english. Plus all the interactions in my native language.
That's a LOT of language practice. That's almost 1800 hours on vocabulary alone. Add on 1500 hours for essays. That's approaching 3200 hours which strongly exceeds the amount of time required to gain general proficiency in a Category V language (2200 hours). That's almost 10+ hours per week on top of school hours themselves.
How many people ever put in that amount of effort into a second language? How many people have the time to put in that amount of effort into a second language?