Very labor intensive (costly) to install, interferes in the appearance of the lawn for a significant time after installation, difficult to “repair”, susceptible to damage with any digging or aeration equipment, holes in drip line more likely to be clogged with roots.
What is the advantage you seek? Reduction in evaporation of water? For most homes, rotating micro sprayers provide better coverage, less run off than traditional spray heads, less aerosolization during application, longer range of throw (up to 25’), allow more spray heads on a single feeder line, and are very easy to maintain. Narrow strips can be handled with appropriate spray heads tailored to that purpose.
With a smart controller, typically watering times for lawns are only once per week in San Diego, less in the winter. With only once or twice a week watering, there is no problem complying with any water restrictions for watering dates in force, although rotating micro heads with smart controllers are generally exempt from such restrictions anyway.
18" spacing is not likely to be close enough to prevent growth lines from showing in the lawn.