"Screen time" is also a great motivator to learn any language, if the fancy entertainment on the screen you'd like to understand is in a language you don't yet understand. (Similar effects apply to the written communication, of course.)

However, this is coming from my "learning a new language as a teenager / adult" experience than "raising bilingual kid" viewpoint, but it seems sensible that it would be also a powerful incentive for small kids, too.