A question has been asked at another forum. We accept Allah preserves the Quran by protecting it's words. Why did Allah not choose to preserve it's meanings?
We have the issue of each sect interpreting the Quran i'ts own way. This is not limited to different sects alone. We even have Quran Centric believers arguing about meanings of different words, concepts, ayahs, etc. For example, some say no to Salat the prayer. Others say yes, but limit it to three prayers. Some argue for 5 prayers. Some find the method to pray in an unbroken 1400 year old practice. Others find method of prayer in the Quran. Same is the case for proper definition of Zakat and Hajj.
On different Quran based forums, there are fierce debates going on over it's interpretation and the proper lexicon meaning of different terms.
How could we ever hope to come to an agreement and unite? When Allah's Messenger is with them, people are able to refer their differences to him. Once a Messenger passes on, things run fine for a while then differences and disputes over proper interpretation of Deen raise their head leading to accusations, conflicts, and even war [which continue to this day, whether it is Judaism, Christianity and Islam].