It is. People who have to resort to drinking bottled water because the tap water is unsafe do live in a third world country.
Draw whatever conclusion from that that you like.
To be fair even in a first world system it's a good idea to filter drinking water again before consuming it. A countertop filtration system is much less expensive than one month of OP's bottled water. $80-200 for the initial setup, $30 every six months to replace the filters... cheaper than $60/mo, probably produces cleaner water in most cases.
That is due to coliform contamination, though. Those countries have feces in their water supply directly and in huge amounts.
What first world country is free of this type of water contamination?
Antarctica. You drill down into some millions-of-years-old chunk of ice and drink that.