why both water tower/with pump and well

Was thinking about do some new prop for my farm and it hit me. What is the well for and would the pump tower not be using well cap on a well.

to my knowledge the well is for the farmers.... they get water from the well to water the crops

looking more at this, basic there is 2 wells but not . NPC use well to get water. Then water crops. But water tower used to auto water but NPC cant get water from it. Now this is where I am lost well is need for NPC to water and tower need for auto water. So why do i need both.Why cant NPC get water for tower.

Wells are items that produce something over time and allow you to take out that product as long as the level is high enough. So the well, seawater pump, yeast & rennet containers etc are all 'wells' Wells don't need any input to work and give the one product when touched.
The NPC farmer by default goes to and uses the SatyrFarm well but can be set to use other water sources however it can't be set to use a water tower since when you touch those it gives a menu rather than directly giving water (which is what the NPC expects).

Water towers are similar to wells but they do need an input of either 'wind power' or electricity depending on type. As mentioned they give water via the touch menu, but also they give water to animal feeders and plants when those items ask for it (via a 'messaging' system)