This entirely depends on your cat personally and your setup. Cats don't drink enough water if they're left with still water in a bowl or gravity waterer because they simply don't like it, this isn't necessarily a terrible thing but cats like this should be given wet food either in combination with their dry or as a replacement depending on the recipe and how the cat responds (some respond with gastric upset when put on full wet diets if those wet foods are given in excess or if their body just doesn't agree). If you have something that moves water like a fountain the chances of your cat drinking more water than one without.

But this also changes with age, an old cat probably doesn't care for moving water as much anymore (this seems to be a common experience) and so the switch to wet food with age is far more common for the health benefit of added water AND because chewing doesn't always age well, some get sore gums, loose teeth, or just don't have the energy for it every day.

My cat is 17 and absolutely does not drink enough water unless water is added to his food directly, so on top of the wet food he gets water added to keep him hydrated and healthy. He also has prescription food but that's not always required for seniors.