Asalamu alikum brothers and sisters,
Actually that was a very good question and you guys also given great answers.
In fact Allah (swt) have sent down revelation in accordance to the time, for example at the time of Mosa (PBUH) Magic was ruling around the world, so Allah (swt) also gave him the same miracles The Magic Stick.
At the time of Esa (Jesus ) (PBUH) may be diseases were common... therefore Allah (swt) gave him a miracle which he could cure any disease.
Now the time of Prophet Mohammad (PBUH) arrived. A time of knowledge and poetry, and also Allah (Swt) wanted to send the last and final revelation to the world so that the people abide by forever.
Hence Allah (swt) send such a book to this world which can solve any problem and also challenges the Science. Now if you read the holy Quran you will find scientific facts which are discovered recently by modern technology like for example.
Going to space
Expanding of Universe
The spherical Earth
and many more...
for more miracles in the Holy Quran please visit: www.miraclesofthequran.com and www.quranmiracles.com
Thank you very much.