I think there are a number of factors in play here. Firstly a lot of people eat a lot more pre-prepared food, take-away, restaurant and cafe food than they used to and guess what? It contains a lot of salt because salt makes things tasty and is mildly addictive, so you buy more of the product and even better it makes you thirsty so you buy drinks as well. I am a bit of a nut-bag about reading ingredients on packets and am frequently horrified at the salt content - and sugar content. Probably very sugary food makes you drink more as well. Then of course there is the need to market bottled water and sell it.
Having said all that I do recognise that you dont always feel thirsty when you get older, but you might be dehydrated. I was on holiday last year in Cuba and the tour rep was crazy about making us drink. Found out one day that a client of the company had died fairly recently on holiday from dehydration, so it is perfectly possible. They were avoiding drinking in case they had to use the dire toilets and they hadnt felt thirsty.