Why should miracles be important to prove, or to serve as an evidence for the truthfulness of a Prophet?
Miracles did take place in the time of Last Prophet, as per sound narrations and consensus of ulema. Miracles did take in the times of Prophet Moses and Isa. It's very curious to know how the magicians/illusionists of Firoun's responded to Prophet Moses' miracle that was granted to him by Allah: they accepted Prophet Moses as Messenger of Allah and recongized his miracle to out of this world! That was nothing short of an experimental testimony.
However, i was puzzled by this statement of Imam Ghazzali in his autobiography: if a person was come to me and say 2+1 = 10; and he'll prove the truth of this statement by turning a stick into a snake - i should never lose certitude in my knowledge that 2 + 1 = 3 and not 10.
Hence, can a rational person [not rationalist per se] demand miracles? The miracle we need to believe in today is: "... Islamic view of a universe created by God, where the trees and the stars worship their Creator, and the sun and the moon follow exquisitely designed laws." And the only time when veils were removed from the people, as public, was the time of Prophets, when trees and stone would talk to Prophet.
We should also know that the nations which self-abdicated themselves, like that of Saleh, requested miracles of their choice. When those miracles were performed, even then they didn't accept Islam. This is true for the scientists of today. Dr Asad Zaman in his brief essay Big Bang writes:
"Sometimes, the evidence is so strong that it breaks through the barriers of unbelief. For example, one of the discoverers of the genetic basis of human life, Crick was quoted as saying, ‘An honest man, armed with all the knowledge available to us now, could only state that in some sense, the origin of life appears at the moment to be almost a miracle, so many are the conditions which would have had to have been satisfied to get it going.” Very unwillingly, against his atheistic beliefs, Crick gave testimony to what the Quran (Surah Al-Waqi’ah 57-58) asserts as challenge: In the creation of man and the seed from which man is created are signs which cannot be denied by those who reflect. Just like many nations mentioned in the Quran, Crick continued to deny God even after witnessing the miracles of creation."Apart from the so-called supernatural miracles, the evidences regarding the coming of the last Prophet is of utmost importance. Please read the chapter on Bahira the Monk in Martin Lings Muhammad.
For me, miracles are an important testimony and evidence. They happen today with the righteous ones. Moreover, it is hard evidence for a very strong alternative view of physical world. It is anti-dote to a mechanistic view of things, which 'cuts the hand of God his creation'. However, with the very miracle of life, my own being and the tree that grows out of the earth naturally, is enough a proof for me. One should also know that Dajjal will use real life CG effects to show miracles to people and claim to be Divine.
Disclaimer: Allah knows best. These thoughts are still very pre-mature and at least some parts are doubtful to me too.