How listening in English promotes other English language skills

The actual process of oral communication consists of two integral parts: listening and speaking.

People develop not only listening comprehension skills in English by watching English movies (films) and other programmes on video, on TV or on the Internet, or by listening to BBC English, the Voice of America and other programmes, and to audio/video recordings for learning English.
People also listen to and learn different accents and peculiarities of English usage in real life settings in different English speaking countries by native English speakers in terms of pronunciation, grammar, vocabulary and style (formal and informal English). Informal English includes colloquial, slang and dialectal usage.

Regular long-term listening to various authentic English audio and video materials helps a learner produce his or her own sentences more quickly and with better wording when speaking than without adequate practice in listening comprehension in English.

Listening practice in English is also very important because foreign learners of English living and learning English in non-English speaking countries have limited opportunities for regular long-term oral communication in English with native speakers of English on a variety of topics and issues using comprehensive content and extensive vocabulary.

And both listening and speaking content of various topics and extensive vocabulary can be covered in practising listening comprehension in English (for example in listening to dialogues, discussions, debates, interviews, narrations, etc).

It is a good idea to practise speaking and discussions of issues in English after listening to texts and programmes in English.
Speaking in English requires from a learner to combine his or her pronunciation, grammar, vocabulary knowledge, thinking over word and phrase choices (and good listening comprehension skills when conversing) to say good sentences as to their content.
Even native speakers of English may experience some difficulty to express their thoughts accurately, precisely and most appropriately in particular contexts. Skillful impressive speaking using the most appropriate vocabulary is an art that many people (including native speakers) lack.
Therefore speaking in English is quite challenging and more difficult for foreign learners than listening comprehension in English.
Foreign learners of English generally have more opportunities for practising listening comprehension in English than for speaking in English.
When a learner listens to English, he or she does not have to create (to construct) in mind and to say own sentences in English like in speaking, but has to understand the content of sentences said by English speakers. The points mentioned above may explain why for most learners it is easier to practise and to develop better skills in listening comprehension than in speaking English.