Some people use miracles to reinforce their belief that G-d is with us and is helping us to do his commandments and retain our Jewish identity.
Others, unfortunately use miracles as an excuse to be lazy. They say for example, if G-d wants us to rebuild the Temple he will bring it down from heaven by a miracle and in the meantime let's not anger the Muslims by looking for natural ways to restore the Temple service.
To avoid this attitude of the lazy Jews, I believe some good Jews are tempted to downplay the oil miracle.