Why does Allah mention stories of previous messengers and prophets in the Quran?

In a Nutshell: We were created as “a vicegerent on Earth”; beginning with Adam (as) vicegerents, messengers and prophets, have appeared throughout human history. The believer should endeavour to derive benefit from contemplation and reflection on their stories.  The Quran frequently makes mention of stories of previous prophets and messengers especially in the Meccan verses. Musa (as) is mentioned 136 times, Ibrahim 69 times Nuh 43 times, Lut 27 times, Yusuf  27 times, Isa 25 times, Adam 25 times, Harun 20 times, Sulayman 17 times, Ishaq 17 times Dawud 16 times, Yaqub 16 times Ismaeel 12 times Shuayb 11 times Salih 9 times Zakaria 7 times Hud 7 times Yahya 5 times Muhammad 4 times Yunus 4 times Ayyub 4 times Idris twice Alyasa  twice Elyas  twice Thul Kifl  twice Qasas is derived from the Arabic word of Qis, which means following a track. Qasas is the plural form of Qissa (story) which is some news that is being told and mentioned continuously (Ragheb e Esfahani, p.671). In the Larose dictionary, qissa (story) means speech, news, chronicles, tale according to the usage of the term in Arabic (Jar, 1387, Vol. 2, p. 1643) The majority of citations are to support the messenger in his quest for the establishment of Allah's deen in society by showing him previous messengers underwent similar ordeals. لَقَدْ كَانَ فِي قَصَصِهِمْ عِبْرَةٌ لِّأُولِي الْأَلْبَابِ مَا كَانَ حَدِيثًا يُفْتَرَىٰ وَلَٰكِن تَصْدِيقَ الَّذِي بَيْنَ يَدَيْهِ وَتَفْصِيلَ كُلِّ شَيْءٍ وَهُدًى وَرَحْمَةً لِّقَوْمٍ يُؤْمِنُونَ Indeed in their stories, there is a lesson for men of understanding (Qur'an 12:111) وَكُلًّا نَّقُصُّ عَلَيْكَ مِنْ أَنبَاءِ الرُّسُلِ مَا نُثَبِّتُ بِهِ فُؤَادَكَ وَجَاءَكَ فِي هَٰذِهِ الْحَقُّ وَمَوْعِظَةٌ وَذِكْرَىٰ لِلْمُؤْمِنِينَ We tell you the stories of the Messengers that we may make firm your heart (Qur'an 11:120) نَحۡنُ نَقُصُّ عَلَيۡكَ اَحۡسَنَ الۡقَصَصِ بِمَاۤ اَوۡحَيۡنَاۤ اِلَيۡكَ هٰذَا الۡقُرۡاٰنَ ​ۖ وَاِنۡ كُنۡتَ مِنۡ قَبۡلِهٖ لَمِنَ الۡغٰفِلِيۡنَ‏ We relate to you, [O Muhammad], the best of stories in what We have revealed to you of this Qur'an although you were, before it, among the unaware. (Qur'an 12:3) What distinguishes a prophet from a messenger was a messenger called his wayward or lost qawm (nation) to submit to Allah whilst a prophet was sent to nations in submission to manage their affairs. Therefore a messenger required a new sharia as the old was lost by their nation, whilst a prophet adhered to the sharia of the previous messenger that was still preserved. Read further details here. Whilst every messenger had a different sharia: ​ؕ لِكُلٍّ جَعَلۡنَا مِنۡكُمۡ شِرۡعَةً وَّمِنۡهَاجً For each We have appointed a divine law and a traced-out way... (Qur'an 5:48) each messenger had the same call to his qawm (nation) to implement Allah's sharia. The emphasis of the stories then show how each messenger undertook his call so lessons can be gleaned from it: These lessons are then a distinct phenomenon from sharia, termed ibra' - and do not only appear in stories of previous messengers but in anything we choose to reflect upon in the universe: وَ اِنَّ لَـكُمۡ فِى الۡاَنۡعَامِ لَعِبۡرَةً​   ؕ نُسۡقِيۡكُمۡ مِّمَّا فِىۡ بُطُوۡنِهَا وَلَـكُمۡ فِيۡهَا مَنَافِعُ كَثِيۡرَةٌ وَّمِنۡهَا تَاۡكُلُوۡنَ And indeed, for you in livestock is a lesson. We give you drink from that which is in their bellies, and for you in them are numerous benefits, and from them you eat. (Qur'an 23:21) The Prophet is quoted as saying: Verily God has ordered me to make my speech, remembrance; and my silence, contemplation; and [what I look at], a lesson As an example, the Ummah today needs to trust in and rely upon Allah as his vicory is near. Allah has plans for the believers and will grant them success, despite giving momentary respite to his enemies: (They were reprieved) until, when the Messengers gave up hope and thought that they were denied (by their people), then came to them Our Help, and whomsoever We willed were delivered. And Our Punishment cannot be warded off from the people who are Mujrimun (criminals, disbelievers, polytheists).” (Qur'an 12:110) A’ishah (ra) explained the above verse in the following words, This verse is concerned with the followers of the Messengers who had faith in their Lord and believed in their Messengers. The period of trials for those followers was long and Allah’s help was delayed until the Messengers gave up hope for the conversion of the disbelievers amongst their nations and suspected that even their followers were shaken in their belief, Allah’s help then came to them.” [Tafsir Ibn Kathir] Allah grants victory when the situation appears hopeless and hardships prevail. Conclusion We were created as “a vicegerent on Earth”; beginning with Adam (as) vicegerents have appeared throughout human history. The believer should endeavour to derive benefit from everything that is around them, and through history, through contemplation, reflection, and connexion. This includes contemplation and reflection on stories of previous messengers and prophets,