Rainwater harvesting is a good thing but it's not all that important to harvest rainwater as most people make it out to be.
Even if you do not harvest the rainwater that falls from the sky the water is still gonna be available for use years later through water wells and streams.
The water that falls from the sky is always being stored and collected naturally through streams, rivers, creeks and even water wells.
The water that falls into the ground eventually goes into arteries into the ground which can then be drilled into and a pump can bring that well water up from the ground.
So the ground is a natural collector and storage tank for rainwater.
If you have a water well on your property the rainwater that falls from the sky goes into the ground and that water that you bring up out of your water well was stored in the ground from the natural rainwater from the sky.
So by collecting rainwater you're really not doing much good for the environment or making the environment better but it's still a good thing to collect rainwater for use such as washing your car, watering your garden, flushing your toilet and much more.
Because that water is already available to you form water storage tanks after you collected it but the ground does act as a natural water filter to clean and disinfect water.
Still most rain water is very safe to drink and doesn't really need filtered or cleaned.