Japanese people don't have a lot of chances to use English, so there are a lot of people who can't speak.
ご質問ありがとうございます。
「機会」はchanceとopportunityに訳せます。こんな話では両方を使えます。「機会が少ない」はnot a lot of chancesとかhave a lot of chancesとかare few chancesなどに訳せます。
例文:There are few chances for Japanese people to use English, so many people can't speak it.
ご参考になれば幸いです。