Something I've actually realised is that I've used maps extensively as a fundamental part of my worldbuilding. It might be in part because I'm a pretty visual person (unsurprising, given my line of work!). It's also in part because of my obsession with realism.
Take, for example, the local militia in a part of my book. To write about them having their yearly drill training, I have to know how many of them there should be, but to know that I have to know population demographics for the local area.
That's where a detailed, accurate map becomes critical. My master regional map is deliberately at a scale of 1 pixel to 1 km to make determining distances and area easier. Photoshop has a function that tells you the total number of pixels in a selection. I can use this to determine the area of a region.
In the case of this example, the region comes out at 1,475km^2. It's not particularly great farming land, and has a population density of only 35/km. The total population is 51,625.
I know 34% of any given population is males of militia age, so I know the total size of the local militia is 17,553. They're further divided into two training areas, so in the end I know my militia drill has to include 8,023 men and boys.
Now, had I just guess blindly, I would have come up with a far smaller number; probably in the hundreds. Training 8,000 men at once is a pretty significant undertaking, and totally changes how the scene plays out.
Without the map I'd never have that realism.
Another smaller-scale example was the village where the protagonist lives. Your typical fantasy village is highly unrealistic; comprising a dozen buildings or so. In reality a typical medieval village averages around 700 people, with some much larger.
It wasn't until I actually sat down and mapped out how many houses you'd need for ~700 people that I realised how big a village needs to be. This particular village has the traditional layout of houses arranged around the commons, but to achieve this the commons is about 300m long and 120m wide. Again, this dramatically changes how I write the story, and it was only possible because I had a detailed map.