It’s not a conspiracy, it’s to do with how they put together the 3d imagery. You can see the same effects on roads in 3d which are largely absent of traffic and people. They use imagery from multiple passes and in some cases laser scans, and these might not be taken at the same time or even on the same day. The result is that when the data is stitched together, items that appear in one data set and not another are screened out and don’t appear in the final images.
If you switch between 2d and 3d in google maps (click on the globe in the corner) you can see that there are many more cars in the 2d version than the 3d one.
Here’s a partially removed aircraft that shows in the 2d, but not in the 3d:
They may not be using the same techniques everywhere though - here is one of the aprons at Heathrow, complete with 3d modelled aircraft: