And it isn't really needed. If you just toss something like that in that isn't implemented well and is just for show other than to boost crop growth, you will have a lot of complaints. If you add irrigation, it has to be done well, and that means stuff like was mentioned. In the end, not worth it. Farming is already unlimited in potential beyond time and space.
Not to mention, if you can bring water to your farm but not to drink, that would further upset people who don't like the water changes, so wouldn't be smart for TFP to do unless they want to change water, which they don't seem interested in doing.