not only are there "still" many asteroids to be found, but there are a lot of asteroids out there. and a lot of them we can't see until they're close enough to the earth, and which upon if discovered we won't be able to do anything about them - when they arrive from the direction of the sun, the sun's luminosity takes away our ability to see them coming, only when they're already here do we see them, and if we do see them, there's no time to do anything about them.

what's more disturbing is that every year the earth passes twice through a meteor stream. a meteor stream which we haven't detected all asteroids in it. asteroids big enough to cause an almost civilization-wiping event.

one of these asteroids from this meteor stream hit the earth about 12 thousand years ago, and some propose that it's what cause the end of the ice age, and ending a past, global civilisation we aren't aware of. the meteor, having hit the polar cap, melted the ice-covered north of the planet ending the ice age.

so i agree with you, more observations need to be made, from the planet's surface but also from orbit, and an asteroid defense system be at the top of every governments' list of defense priorities.