Seal Coating your asphalt is necessary in order to prolong the life of your driveway or parking lot. It acts as a barrier protecting the underneath asphalt. It also conditions the Asphalt to minimize cracking and loose gravel.
The crack filling doesn't make cracks vanish but does slow the cracks from getting worse. Crack filling and seal coating your asphalt is a great way to make old pavement look new again.