Allah Almighty states in the Qur’an:

“And I did not create the jinn and mankind except to worship Me. I do not want from them any provision, nor do I want them to feed Me.  Indeed, it is Allah who is the [continual] Provider, the firm possessor of strength.” Surah Dhariyat, chapter number 51, verse 56.

As mentioned in this verse human beings were created for the sole purpose of worshipping Allah Almighty. Worship (Ibadah) in Arabic means subjugating or lowering oneself which is derived from the root word (Abd) servant. In Islamic terminology, worship has a very comprehensive meaning: total obedience to Allah alone out of love for Him. It comprises of the actions of the heart and limbs to please Allah which are ordained by Allah. As human beings, we are not in a position at our level to fully comprehend Allah’s wisdom in His decisions and His jurisprudence. We just make our best effort to understand His commandments with what knowledge we have. He ordained His worship on us because He knows out of His profound knowledge and wisdom that worshipping Him would only benefit His creation and make them the best possible human beings – as He wishes them to be. 
Allah Almighty states in the Qur’an:

“O mankind, you are those in need of Allah, while Allah is Free of need, the Praiseworthy”. Surah Fatir chapter 35, verse 15.

Our worship to Allah Almighty does not benefit Him in any way as He is above and beyond His creation. He is limitless and free from need while His creation is completely dependent on Him. Allah wants us to worship Him not out of the need for our worship, but because He knows that worshipping Him will benefit His creation. Here are a few examples:

First and foremost, worship is the best way to stay connected to Allah, our creator, and to focus on our relation with Him which one tends to forget due the distractions of this life.  He created us as intelligent, moral beings with the freedom to choose between right and wrong while lighting up the path to success for us through guidance that would lead us to prosper in this life and hereafter. Through worship one is able to recognize and acknowledge the greatness of Allah Almighty and appreciate the blessings He has showered upon us. Allah Almighty loves us and He loves to hear from us as mentioned in the Quran.

And Allah loves the doers of good”; Surah Aal-e-Imraan, chapter 3, verse, 134.

And when My servants ask you, [O Muhammad], concerning Me - indeed I am near. I respond to the invocation of the supplicant when he calls upon Me. So let them respond to Me [by obedience] and believe in Me that they may be [rightly] guided”. Surah Baqarah, chapter 2, verse 186. 

So, a Muslim understands that worship is a means of the constant reminder of Allah because He is always near to us and He is the one Who guides us to become better people and achieve success, and prayer is a source of communication between God and the worshipper.

Say [O Messenger of Allah], "O mankind, the truth has come to you from your Lord, so whoever is guided is only guided for [the benefit of] his soul, and whoever goes astray only goes astray [in violation] against it. And I am not over you a manager." Surah Younus chapter 10, verse 108.

Secondly, Allah ordained His worship on us to benefit us out of His Benevolence. One can understand this point through the example of a doctor who prescribes medication for his patient in order to treat him. If the patient takes the medication following the advice of the doctor, it will benefit him, not the doctor. In the same way, Allah has ordained His worship on us to benefit us as it boosts one’s belief and gives one the strength, hope and drive to overcome difficulties while walking on the right path which has been designed for our own prosperity. He calls upon us to worship Him because it allows us to attain self-actualization, a clear moral foundation, and develop ourselves as successful human beings – all of which are benefits not to Allah Almighty, but rather to our own selves. 

Thirdly, the heart feels peace and tranquility through Allah’s praise and remembrance however deep within hardships one may be. His remembrance strengthens the hearts and gives one courage to face the challenges this life puts forward and leads to inner peace. Allah mentions in the Qur’an:

“Those who have believed and whose hearts are assured by the remembrance of Allah. Unquestionably, by the remembrance of Allah hearts are assured." Surah Ra’d chapter 13, verse 28.

Allah’s every decision is based on His knowledge and wisdom. He created mankind as the noblest of all His creations whom He loves more than any other creation of His. For this very reason, He ordained worship upon us as it enables us to become the best versions of ourselves through our actions while staying connected to our Lord. Allah knows best. May Allah guide us.