There are good reasons for having your own water supply:
It pays for itself in savings of water bills. With your own borehole you are allowed 20,000 litres per day without applying for a licence, so the water supply is free. (A typical house uses several hundred litres of water a day.) There is plenty for all the households in the UK.
You get clean water (subject to testing) that has not been recycled or chlorinated. This is healthy for you, your children and animals.
You may wish to sell the water to neighbours or share the investment with them (the cost of a working borehole is normally £5000 upwards. You pay the driller for the hole, not the water. If the hole is dry, you still pay. That’s why it’s so important to employ a dowser; the risk of wasting money on dry boreholes is virtually eliminated.)
In large areas of parkland, having your own water supply (and suitable equipment) can be very useful in fighting fires.