Your carpets could also be wet due to leaking door seals. That is, they have shrunk.

Here is a tried and true way of testing if you have cabin leaks. Go to a carwash bay, put your air conditioning on high, and get out of the car (while it is still running), and shut it up (don't lock yourself out!!!). Hose it down real good with soapy water, getting it around the seals.

Watch for air bubbles forming.

Where bubbles form...is where air is coming out. Which is where water will go in when the cabin isn't pressurized or equal pressure, and where you will hear whistling when the vehicle is on the highway.

Used this method to track down noises and leaks at a body shop I used to work at.

The problem is that there are many areas air can come out that will not be a water leak in the worst circumstances. Even my door handles blow bubbles if I wash the car while it idles. But they never leak.

There are rain gutters and channeled weatherstripping that don't have to be air-tight to prevent water leaks.

Simply adjusting your door seals to account for shrinking should solve most leak problems that aren't caused by a sunroof drain.