I don't get this. I'm trilingual, and I think in English, but I'm fluent in the other 2 languages as well. My parents converse in the mother tongue at home, but with friends they would switch to another language. I think parents are vastly underestimating the cognitive powers of young children.
Some parents are probably just trying to shield their children from what they see as a handicap, or a source of embarrassment. They're wrong, but their motivations are understandable.
(And if they're in a very cloistered community, their parents are probably more focused on the native language instead of the host language anyway.)
I was surprised to hear my son (at the time only four) say "Hiro is the hero Big Hero 6." Pronouncing both Hiro and hero correctly.
Is that really a thing? My father is japanese and I grew up in Brazil. I don't think my lack of fluency in japanese was due to any fear from my parents - my parents spoke japanese at home and even had me attend nihongakkou (japanese classes). But it's very hard to develop real fluency without a community. My cousins had always been more fluent due to being involved in a karaoke community - something my family wasn't. My mother was born in Brazil too, and spoke japanese fluently as a child because she was raised in a isolated japanese farming community where many people couldn't speak portuguese.
Even now, with my kids, it's been far easier for them to pick up mandarin (my wife's mother tongue), since until a few months ago, their grandparents lived with us and spoke mandarin exclusively, and since the community where we lived was predominantly chinese (read: there are chinese supermarkets, there are chinese books in the library, and most classmates in their school are 1st/2nd-gen chinese). Compared to that, it's been a lot harder to get them to learn portuguese, since I'm literally the only person around them who speaks it.
I thought about this a little more, and yes, community did help me develop my mother tongue a lot. There were the parents who exclusively spoke the language, but I would frequently visit my grandparents, who would also speak it. And they would take me to visit other members of the clan, who would also speak that. Perhaps it is a diversity of people speaking the language that gives one a certain amount of fluency?
I learned Hindi because it is the national language and my peers in school usually conversed in it. English was what most books were written in and it was the language of instruction. So it seemed very natural to be fluent in multiple languages.
Something that worked well for me was making it a game when the kid wasn't expecting it. The first time was over breakfast. I brought a boogie board and told him we were gonna learn some portuguese. I drew a happy chubby boy and asked him who it was. He shrugged. I told it was him. Now I had his attention, so I drew a strawberry and asked him what that was. Once he answered, I told him "yes, morango". Then, I drew him eating it and said "Calvin come morango" (pointing to him and the strawberry as I said the respective words). Then, I said "Calvin come..." and picked up a real strawberry. Now, the exercise was kind of a guessing/memory game for him. I only covered a few words and it involved a lot of repetition and high fives, but he became a lot more open to the idea of learning portuguese after that.
When my kid was learning to read, making some flash cards also worked really well - drawing on one side, word on the other. The trick is in making a few verb ones, and nouns that can complement, plus one with a drawing of the kid, then do permutations, e.g. "Calvin come bolo" (cake), "Bolo de morango", "Calvin come bolo de chocolate", etc. "Eat" is a good starting verb, "go" is also very versatile in combination with types of vehicles and places, then you can try expanding to other daily things.
Would love to hear how that works for others
As we're in Finland I assume that he'll have a Finnish accent when he gets a bit more proficient, but so far things seem to be working out. I expect he'll learn English pretty well, partly via me, but also via random conversations, TV, etc.
One of the pleasant surprises were that his first two words were "Daddy" and "Äiti", respectively.
I have been wondering if education in a single language is not a inhibitor of development much beyond anything that we can presently suspect. My pathetic reading of history places human development where either languages are daily flux, along trade routes, else in close proximity and contact even as created in wartime alliances. How easily do we attribute to the national character our perception of intellectual capacity and style. The joke about Hungarians being perforce genii the complexity of their language demanding that agility. So should I expose my infant son to as many spoken languages as possible for the longest time?