ND4 and ND8 provide plenty of light to stop movement with an available f2.8.
Really? That might be true on a bright sunny day ...... but ..
Here's an example of a moving subject shot at 1/120 at f2.8 & ISO 200.
The ship is making 17 knots (20 mph or 31 km/h).
At 1/120th it's only just fast enough to get an acceptable result.
How's that going to come out at 1/30th (ND4) or 1/15th (ND8)?
I think most here are smart enough to take off the NDs in really dim light.
Going by the responses here, I'm not so sure about that.
And there are many beginner photographers trying to learn things here and getting incorrect ideas.
I have shot with an ND4 after sundown.
Maybe you just shoot buildings.
Many have to contend with moving subjects or trees blown by the wind etc.
Leaving the ND filter on your camera when shooting stills isn't going to do anything to help your photography (beyond the much over-mentioned wispy waterfalls and car light trails.
Unless you have a particular reason to want to force a slower shutter speed, it makes no sense to use ND filters on your drone camera.