Because individual emitters only water small areas around each emitter, only a fraction of the soil's surface is moistened. This translates to fewer weeds because water doesn't go where you don't want it. The components for a drip system are inexpensive and, possibly best of all, simple to install. I converted a traditional underground sprinkler system to drip, utilizing the existing pipes. All I did was replace the regular sprinkler heads with rubber tubing and individual emitters.
Emitters vary as to how much water is released.
About the biggest problem with the system is maintenance. Due to hard water and debris clogging the narrow tubing and tiny emitters, clogging often occurs. It requires constant checking and flushing. I always have extra emitters and tubing on hand. Also, it's difficult to actually see drip systems working.