It is not laziness.
I am bilingual, so my is DH and both sets of our parents. Both my DM and my MIL could be said to have English as a second language.
What a lot of people don't seem to realise is the continual exposure you need to a language in order to keep yourself reasonably fluent. My MIL constantly listens to radio in her mother tongue because, otherwise, living in Britain full time and speaking English 90 percent of the time, her ability in her mother tongue starts to disappear. She forgets more uncommon verbs and cannot remember the nouns for certain objects.
I find it myself. I suspect I've lost up to 60 percent of my second language ability over the last five years, purely because I rarely watch a film or have a conversation in the language these days. If you don't use a language, it starts to vanish from your brain.
So it's very difficult for people in Britain to learn another language to fluency and keep it if they do not have a parent or spouse that is fluent in the tongue because Brits have so little environmental exposure to other languages. In other countries, English can be found everywhere: from road signs and billboards to adverts, films, TV series, imported food products and pop songs in cafes.
Add to that the difficulty of learning a second language when you haven't been taught grammar (it's pretty impossible to understand how my second language works on a very basic level if you don't have a grasp of certain grammatical concepts, such as the subject and object of a verb), and it's hardly surprising that Brits find learning another language extremely difficult.
What I do find interesting ~ and if I ever went back into academia, I might consider doing some sort of research project on this ~ is how a lot of kids struggle with MFLs at school, but yet seem to pick up coding and programming relatively easily. I do wonder if there is something you could take from the motivations and environment surrounding the learning of code and apply to MFLs in some way.
I know code doesn't require speaking or listening skills, but the concepts of communication in an alternative string of characters in order to achieve a goal are ostensibly identical.