Have you ever seen Bond doing something without purpose? So why would he just wear eyeglasses without any reason? Eyeglasses, aka spy Glasses, of a spy ought to have some other functionality than just protecting eyes or adding up fashion.
And that exactly we have seen in The World Is Not Enough, the 1999 Bond film. Here 007 used a pair of spy glasses that could detonate an explosive remotely and enabled X-ray vision. However, X-ray glasses were also seen in the movie Casino Royale released in 1966 but that was owned by the villain Le Chiffre.
In the Pierce Brosnan era the utility of the spyglasses was much improved with the advent of technology. Bond had a pistol that holds some explosives and with the spyglass he detonated that flash-bang charge. He also used the X-ray vision enabled glass later on to find out if the enemies had any concealed weapons or not.