Salah is the major form of worship that a Muslim offers five times a day regularly. It is an obligation upon a Muslim and a Muslim is to offer no excuse when it comes to offering Salah. The offering of Salah in addition to representing the submission of Muslims to their Lord also has other benefits as well which are highly cherished by every Muslim.

The establishment of Salah is one of the major topics upon which Quran has emphasized more than anything else. In Quran Allah Almighty has stressed upon Muslims to learn to offer Salah regularly and with mentions of offering Salah Allah has also mentioned its benefits with it as well. The lines below give the major benefits of Salah that elaborate the importance of Salah.
Invoking Allah:

Although there is no constraint upon a Muslim on how to invoke Allah Almighty, however, prayer is the preferred means of doing so as when a person worships Allah he or she develops a connection with Allah and any invocation within that or after that connection is bound to be accepted by Allah more compared to invocation done in any other circumstance. In the Holy Quraan, Allah Almighty says:

يَـٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوا۟ ٱسْتَعِينُوا۟ بِٱلصَّبْرِ وَٱلصَّلَوٰةِ ۚ إِنَّ ٱللَّهَ مَعَ ٱلصَّـٰبِرِينَ
“O you who have believed, seek help through patience and prayer. Indeed, Allah is with the patient.” (Al Baqarah 2: 153)
Therefore, a Muslim must use prayers as a means of invocation and ask Allah Almighty for help and assistance in any difficulty or worry.

Leading To Taqwa:
Piety or righteousness is the prime objective which a Muslim has to achieve in this life. All the instructions, constraints, freedom, rights and education provided by Islam are with the objective that a Muslim becomes pious and moves on the righteous path. In this regard, prayer has a great role to play as it promotes Taqwa or piety in the follower. In Quran, Allah Almighty says:

ذَٰلِكَ ٱلْكِتَـٰبُ لَا رَيْبَ ۛ فِيهِ ۛ هُدًى لِّلْمُتَّقِينَ
ٱلَّذِينَ يُؤْمِنُونَ بِٱلْغَيْبِ وَيُقِيمُونَ ٱلصَّلَوٰةَ وَمِمَّا رَزَقْنَـٰهُمْ يُنفِقُونَ
“This is the Book in which there is no doubt, a guidance for those who have Taqwa: who believe in the unseen, and who establish Salah, and spend out of what we have provided for them.” (Al Baqarah: 2-3)
Therefore, in addition to giving charity and believing in the unseen, a Muslim must also establish Salah in order to move towards Taqwa.

Reward in The After world:
Every deed, whether good or bad that a Muslim undertakes in this life, he or she will have to be answerable for it in the afterlife. Although all the deeds get rewarded in the afterlife, however, the actual reward of Salah will truly be realized in the afterlife when Allah Almighty will shower special blessings on that person. In Quran, Allah says:

إِنَّ ٱلَّذِينَ ءَامَنُوا۟ وَعَمِلُوا۟ ٱلصَّـٰلِحَـٰتِ وَأَقَامُوا۟ ٱلصَّلَوٰةَ وَءَاتَوُا۟ ٱلزَّكَوٰةَ لَهُمْ أَجْرُهُمْ عِندَ رَبِّهِمْ وَلَا خَوْفٌ عَلَيْهِمْ وَلَا هُمْ يَحْزَنُونَ
“Indeed, those who believe and do righteous deeds and establish prayer and give zakaah will have their reward with their Lord, and there will be no fear concerning them, nor will they grieve.” (2:277)

Therefore, prayer is not something that ends in this world, rather the real reward of it will come to surface in the afterlife.